Industry Cluster's Adaptive Co-competition Behavior Modeling Inspired by Swarm Intelligence

NASA Astrophysics Data System (ADS)

Xiang, Wei; Ye, Feifan

Adaptation helps the individual enterprise to adjust its behavior to uncertainties in environment and hence determines a healthy growth of both the individuals and the whole industry cluster as well. This paper is focused on the study on co-competition adaptation behavior of industry cluster, which is inspired by swarm intelligence mechanisms. By referencing to ant cooperative transportation and ant foraging behavior and their related swarm intelligence approaches, the cooperative adaptation and competitive adaptation behavior are studied and relevant models are proposed. Those adaptive co-competition behaviors model can be integrated to the multi-agent system of industry cluster to make the industry cluster model more realistic.

Gender differences in testosterone and cortisol response to competition.

PubMed

Kivlighan, Katie T; Granger, Douglas A; Booth, Alan

2005-01-01

This study examined intra-individual change in testosterone, cortisol, and hormone-behavior relationships in response to a rowing ergometer competition. Forty-six members (23 females) of a university crew team provided saliva samples before, 20- and 40-min post-competition, as well as baselines on a non-competition day. Behavioral assessments included measures of previous rowing experience, dominance, competitiveness, bonding with teammates, pre- and post-competition mental state and performance. Men's and women's endocrine responses to this competitive setting were more different than alike and varied by level of competitive experience, the specific phase of the competitive event, and the particular hormone measured. Inter-individual differences in testosterone and cortisol were differentially associated with social affiliation with teammates but rarely with dominance or competitiveness. Theoretically, the findings support the integration of features of the 'tend and befriend' model with the biosocial model of status, and suggest future research directions that may lead to clarification and refinement of those ideas.

Maximum Entropy for the International Division of Labor.

PubMed

Lei, Hongmei; Chen, Ying; Li, Ruiqi; He, Deli; Zhang, Jiang

2015-01-01

As a result of the international division of labor, the trade value distribution on different products substantiated by international trade flows can be regarded as one country's strategy for competition. According to the empirical data of trade flows, countries may spend a large fraction of export values on ubiquitous and competitive products. Meanwhile, countries may also diversify their exports share on different types of products to reduce the risk. In this paper, we report that the export share distribution curves can be derived by maximizing the entropy of shares on different products under the product's complexity constraint once the international market structure (the country-product bipartite network) is given. Therefore, a maximum entropy model provides a good fit to empirical data. The empirical data is consistent with maximum entropy subject to a constraint on the expected value of the product complexity for each country. One country's strategy is mainly determined by the types of products this country can export. In addition, our model is able to fit the empirical export share distribution curves of nearly every country very well by tuning only one parameter.

Maximum Entropy for the International Division of Labor

PubMed Central

Lei, Hongmei; Chen, Ying; Li, Ruiqi; He, Deli; Zhang, Jiang

2015-01-01

As a result of the international division of labor, the trade value distribution on different products substantiated by international trade flows can be regarded as one country’s strategy for competition. According to the empirical data of trade flows, countries may spend a large fraction of export values on ubiquitous and competitive products. Meanwhile, countries may also diversify their exports share on different types of products to reduce the risk. In this paper, we report that the export share distribution curves can be derived by maximizing the entropy of shares on different products under the product’s complexity constraint once the international market structure (the country-product bipartite network) is given. Therefore, a maximum entropy model provides a good fit to empirical data. The empirical data is consistent with maximum entropy subject to a constraint on the expected value of the product complexity for each country. One country’s strategy is mainly determined by the types of products this country can export. In addition, our model is able to fit the empirical export share distribution curves of nearly every country very well by tuning only one parameter. PMID:26172052

Seeing the forest from the trees: Emergence of the competitive franchise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ridley, S.

In present efforts to establish generation markets and transmission access, the participants risk losing sight of the strong consumer presence essential for competition to work. It`s time to move discussion about restructuring to the consumer level and take up the issue of the franchise.

75 FR 4701 - In the Matter of Procedural Amendments to Commission Part 1 Competitive Bidding Rules

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-29

... Procedural Amendments to Commission Part 1 Competitive Bidding Rules AGENCY: Federal Communications... bidding rules. The Commission amends the rule specifying how to report potential violations of the prohibition on certain communications in order to reduce the risk that bidding-related information might be...

39 CFR 3020.32 - Supporting justification.

Code of Federal Regulations, 2010 CFR

2010-07-01

... factors of 39 U.S.C. 3622(c); (c) Explain why, as to competitive products, the addition, deletion, or... change does not classify as competitive a product over which the Postal Service exercises sufficient market power that it can, without risk of losing a significant level of business to other firms offering...

The potential premium range of risk-rating in competitive markets for supplementary health insurance.

PubMed

Paolucci, Francesco; Prinsze, Femmeke; Stam, Pieter J A; van de Ven, Wynand P M M

2009-09-01

In this paper, we simulate several scenarios of the potential premium range for voluntary (supplementary) health insurance, covering benefits which might be excluded from mandatory health insurance (MI). Our findings show that, by adding risk-factors, the minimum premium decreases and the maximum increases. The magnitude of the premium range is especially substantial for benefits such as medical devices and drugs. When removing benefits from MI policymakers should be aware of the implications for the potential reduction of affordability of voluntary health insurance coverage in a competitive market.

Loss of competition in the outside host environment generates outbreaks of environmental opportunist pathogens.

PubMed

Anttila, Jani; Ruokolainen, Lasse; Kaitala, Veijo; Laakso, Jouni

2013-01-01

Environmentally transmitted pathogens face ecological interactions (e.g., competition, predation, parasitism) in the outside-host environment and host immune system during infection. Despite the ubiquitousness of environmental opportunist pathogens, traditional epidemiology focuses on obligatory pathogens incapable of environmental growth. Here we ask how competitive interactions in the outside-host environment affect the dynamics of an opportunist pathogen. We present a model coupling the classical SI and Lotka-Volterra competition models. In this model we compare a linear infectivity response and a sigmoidal infectivity response. An important assumption is that pathogen virulence is traded off with competitive ability in the environment. Removing this trade-off easily results in host extinction. The sigmoidal response is associated with catastrophic appearances of disease outbreaks when outside-host species richness, or overall competition pressure, decreases. This indicates that alleviating outside-host competition with antibacterial substances that also target the competitors can have unexpected outcomes by providing benefits for opportunist pathogens. These findings may help in developing alternative ways of controlling environmental opportunist pathogens.

Risk analysis for rumor propagation in metropolises based on improved 8-state ICSAR model and dynamic personal activity trajectories

NASA Astrophysics Data System (ADS)

Zhang, N.; Huang, H.; Duarte, M.; Zhang, J.

2016-06-01

Social media has developed extremely fast in metropolises in recent years resulting in more and more rumors disturbing our daily lives. Knowing the characteristics of rumor propagation in metropolises can help the government make efficient rumor refutation plans. In this paper, we established a dynamic spatio-temporal comprehensive risk assessment model for rumor propagation based on an improved 8-state ICSAR model (Ignorant, Information Carrier, Information Spreader, Advocate, Removal), large personal activity trajectory data, and governmental rumor refutation (anti-rumor) scenarios. Combining these relevant data with the 'big' traffic data on the use of subways, buses, and taxis, we simulated daily oral communications among inhabitants in Beijing. In order to analyze rumor and anti-rumor competition in the actual social network, personal resistance, personal preference, conformity, rumor intensity, government rumor refutation and other influencing factors were considered. Based on the developed risk assessment model, a long-term dynamic rumor propagation simulation for a seven day period was conducted and a comprehensive rumor propagation risk distribution map was obtained. A set of the sensitivity analyses were conducted for different social media and propagation routes. We assessed different anti-rumor coverage ratios and the rumor-spreading thresholds at which the government started to launch anti-rumor actions. The results we obtained provide worthwhile references useful for governmental decision making towards control of social-disrupting rumors.

Optimizing cardiothoracic surgery information for a managed care environment.

PubMed

Denton, T A; Matloff, J M

1995-11-01

The rapid change occurring in American healthcare is a direct response to rising costs. Managed care is the fastest growing model that attempts to control escalating costs through limitations in patient choice, the active use of guidelines, and placing providers at risk. Managed care is an information intensive system, and those providers who use information effectively will be at an advantage in the competitive healthcare marketplace. There are five classes of information that providers must collect to be competitive in a managed care environment: patient satisfaction, medical outcomes, continuous quality improvement, quality of the decision, and financial data. Each of these should be actively used in marketing, assuring the quality of patient care, and maintaining financial stability. Although changes in our healthcare system are occurring rapidly, we need to respond to the marketplace to maintain our viability, but as physicians, we have the singular obligation to maintain the supremacy of the individual patient and the physician-patient relationship.

Tree growth and competition in an old-growth Picea abies forest of boreal Sweden: influence of tree spatial patterning

USGS Publications Warehouse

Fraver, Shawn; D'Amato, Anthony W.; Bradford, John B.; Jonsson, Bengt Gunnar; Jönsson, Mari; Esseen, Per-Anders

2013-01-01

Question: What factors best characterize tree competitive environments in this structurally diverse old-growth forest, and do these factors vary spatially within and among stands? Location: Old-growth Picea abies forest of boreal Sweden. Methods: Using long-term, mapped permanent plot data augmented with dendrochronological analyses, we evaluated the effect of neighbourhood competition on focal tree growth by means of standard competition indices, each modified to include various metrics of trees size, neighbour mortality weighting (for neighbours that died during the inventory period), and within-neighbourhood tree clustering. Candidate models were evaluated using mixed-model linear regression analyses, with mean basal area increment as the response variable. We then analysed stand-level spatial patterns of competition indices and growth rates (via kriging) to determine if the relationship between these patterns could further elucidate factors influencing tree growth. Results: Inter-tree competition clearly affected growth rates, with crown volume being the size metric most strongly influencing the neighbourhood competitive environment. Including neighbour tree mortality weightings in models only slightly improved descriptions of competitive interactions. Although the within-neighbourhood clustering index did not improve model predictions, competition intensity was influenced by the underlying stand-level tree spatial arrangement: stand-level clustering locally intensified competition and reduced tree growth, whereas in the absence of such clustering, inter-tree competition played a lesser role in constraining tree growth. Conclusions: Our findings demonstrate that competition continues to influence forest processes and structures in an old-growth system that has not experienced major disturbances for at least two centuries. The finding that the underlying tree spatial pattern influenced the competitive environment suggests caution in interpreting traditional tree competition studies, in which tree spatial patterning is typically not taken into account. Our findings highlight the importance of forest structure – particularly the spatial arrangement of trees – in regulating inter-tree competition and growth in structurally diverse forests, and they provide insight into the causes and consequences of heterogeneity in this old-growth system.

Evolving nutritional strategies in the presence of competition: a geometric agent-based model.

PubMed

Senior, Alistair M; Charleston, Michael A; Lihoreau, Mathieu; Buhl, Jerome; Raubenheimer, David; Simpson, Stephen J

2015-03-01

Access to nutrients is a key factor governing development, reproduction and ultimately fitness. Within social groups, contest-competition can fundamentally affect nutrient access, potentially leading to reproductive asymmetry among individuals. Previously, agent-based models have been combined with the Geometric Framework of nutrition to provide insight into how nutrition and social interactions affect one another. Here, we expand this modelling approach by incorporating evolutionary algorithms to explore how contest-competition over nutrient acquisition might affect the evolution of animal nutritional strategies. Specifically, we model tolerance of nutrient excesses and deficits when ingesting nutritionally imbalanced foods, which we term 'nutritional latitude'; a higher degree of nutritional latitude constitutes a higher tolerance of nutritional excess and deficit. Our results indicate that a transition between two alternative strategies occurs at moderate to high levels of competition. When competition is low, individuals display a low level of nutritional latitude and regularly switch foods in search of an optimum. When food is scarce and contest-competition is intense, high nutritional latitude appears optimal, and individuals continue to consume an imbalanced food for longer periods before attempting to switch to an alternative. However, the relative balance of nutrients within available foods also strongly influences at what levels of competition, if any, transitions between these two strategies occur. Our models imply that competition combined with reproductive skew in social groups can play a role in the evolution of diet breadth. We discuss how the integration of agent-based, nutritional and evolutionary modelling may be applied in future studies to further understand the evolution of nutritional strategies across social and ecological contexts.

Risk sensitivity as an evolutionary adaptation

NASA Astrophysics Data System (ADS)

Hintze, Arend; Olson, Randal S.; Adami, Christoph; Hertwig, Ralph

2015-02-01

Risk aversion is a common behavior universal to humans and animals alike. Economists have traditionally defined risk preferences by the curvature of the utility function. Psychologists and behavioral economists also make use of concepts such as loss aversion and probability weighting to model risk aversion. Neurophysiological evidence suggests that loss aversion has its origins in relatively ancient neural circuitries (e.g., ventral striatum). Could there thus be an evolutionary origin to risk aversion? We study this question by evolving strategies that adapt to play the equivalent mean payoff gamble. We hypothesize that risk aversion in this gamble is beneficial as an adaptation to living in small groups, and find that a preference for risk averse strategies only evolves in small populations of less than 1,000 individuals, or in populations segmented into groups of 150 individuals or fewer - numbers thought to be comparable to what humans encountered in the past. We observe that risk aversion only evolves when the gamble is a rare event that has a large impact on the individual's fitness. As such, we suggest that rare, high-risk, high-payoff events such as mating and mate competition could have driven the evolution of risk averse behavior in humans living in small groups.

Hierarchical competitions subserving multi-attribute choice

PubMed Central

Hunt, Laurence T; Dolan, Raymond J; Behrens, Timothy EJ

2015-01-01

Valuation is a key tenet of decision neuroscience, where it is generally assumed that different attributes of competing options are assimilated into unitary values. Such values are central to current neural models of choice. By contrast, psychological studies emphasize complex interactions between choice and valuation. Principles of neuronal selection also suggest competitive inhibition may occur in early valuation stages, before option selection. Here, we show behavior in multi-attribute choice is best explained by a model involving competition at multiple levels of representation. This hierarchical model also explains neural signals in human brain regions previously linked to valuation, including striatum, parietal and prefrontal cortex, where activity represents competition within-attribute, competition between attributes, and option selection. This multi-layered inhibition framework challenges the assumption that option values are computed before choice. Instead our results indicate a canonical competition mechanism throughout all stages of a processing hierarchy, not simply at a final choice stage. PMID:25306549

78 FR 12271 - Wireline Competition Bureau Seeks Additional Comment In Connect America Cost Model Virtual Workshop

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-22

... Competition Bureau seeks public input on additional questions relating to modeling voice capability and Annual... submitting comments and additional information on the rulemaking process, see the SUPPLEMENTARY INFORMATION section of this document. FOR FURTHER INFORMATION CONTACT: Katie King, Wireline Competition Bureau at (202...

Global attractivity of an almost periodic N-species nonlinear ecological competitive model

NASA Astrophysics Data System (ADS)

Xia, Yonghui; Han, Maoan; Huang, Zhenkun

2008-01-01

By using comparison theorem and constructing suitable Lyapunov functional, we study the following almost periodic nonlinear N-species competitive Lotka-Volterra model: A set of sufficient conditions is obtained for the existence and global attractivity of a unique positive almost periodic solution of the above model. As applications, some special competition models are studied again, our new results improve and generalize former results. Examples and their simulations show the feasibility of our main results.

Design logistics performance measurement model of automotive component industry for srengthening competitiveness of dealing AEC 2015

NASA Astrophysics Data System (ADS)

Amran, T. G.; Janitra Yose, Mindy

2018-03-01

As the free trade Asean Economic Community (AEC) causes the tougher competition, it is important that Indonesia’s automotive industry have high competitiveness as well. A model of logistics performance measurement was designed as an evaluation tool for automotive component companies to improve their logistics performance in order to compete in AEC. The design of logistics performance measurement model was based on the Logistics Scorecard perspectives, divided into two stages: identifying the logistics business strategy to get the KPI and arranging the model. 23 KPI was obtained. The measurement result can be taken into consideration of determining policies to improve the performance logistics competitiveness.

Robustness of cluster synchronous patterns in small-world networks with inter-cluster co-competition balance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jianbao; Ma, Zhongjun, E-mail: mzj1234402@163.com; Chen, Guanrong

All edges in the classical Watts and Strogatz's small-world network model are unweighted and cooperative (positive). By introducing competitive (negative) inter-cluster edges and assigning edge weights to mimic more realistic networks, this paper develops a modified model which possesses co-competitive weighted couplings and cluster structures while maintaining the common small-world network properties of small average shortest path lengths and large clustering coefficients. Based on theoretical analysis, it is proved that the new model with inter-cluster co-competition balance has an important dynamical property of robust cluster synchronous pattern formation. More precisely, clusters will neither merge nor split regardless of adding ormore » deleting nodes and edges, under the condition of inter-cluster co-competition balance. Numerical simulations demonstrate the robustness of the model against the increase of the coupling strength and several topological variations.« less

A mathematical model of nutrient influence on fungal competition.

PubMed

Jabed A Choudhury, M; M J Trevelyan, Philip; P Boswell, Graeme

2018-02-07

Fungi have a well-established role in nutrient cycling and are widely used as agents in biological control and in the remediation of polluted landscapes. Competition for resources between different fungal communities is common in these contexts and its outcome impacts on the success of such biotechnological applications. In this investigation a mathematical model is constructed to represent competition between two fungal colonies that have access to different resources. It is shown that the model equations display a multitude of travelling wave solutions and that the outcome of competition between two fungal biomasses can be controlled through the simple manipulation of the nutrient resources available to each. The model equations are also numerically integrated to illustrate the range of outcomes arising from fungal competition and these results are placed in context of established experimental observations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Robustness of cluster synchronous patterns in small-world networks with inter-cluster co-competition balance

NASA Astrophysics Data System (ADS)

Zhang, Jianbao; Ma, Zhongjun; Chen, Guanrong

2014-06-01

All edges in the classical Watts and Strogatz's small-world network model are unweighted and cooperative (positive). By introducing competitive (negative) inter-cluster edges and assigning edge weights to mimic more realistic networks, this paper develops a modified model which possesses co-competitive weighted couplings and cluster structures while maintaining the common small-world network properties of small average shortest path lengths and large clustering coefficients. Based on theoretical analysis, it is proved that the new model with inter-cluster co-competition balance has an important dynamical property of robust cluster synchronous pattern formation. More precisely, clusters will neither merge nor split regardless of adding or deleting nodes and edges, under the condition of inter-cluster co-competition balance. Numerical simulations demonstrate the robustness of the model against the increase of the coupling strength and several topological variations.

Collaborative research in the model spinal cord injury systems: process and outcomes.

PubMed

Richards, J Scott

2002-01-01

To review the way in which collaborative research has been conducted under the National Institute on Disability and Rehabilitation Research (NIDRR)-funded Model Spinal Cord Injury Systems (MSCIS) Program, changes made in that process, and significant outcomes. A comparison of changes by NIDRR in the way collaborative research was competed and funded in the 1 995 and 2001 competitions. A review of outcomes of the 1 995 collaborative projects was based on queries to lead centers. Collaborative research through the model SCI systems has been conducted and continues to be conducted through 2 main venues: The National Spinal Cord Injury Statistical Center (NSCISC) database, which has provided data for a number of collaborative studies, and specifically funded proposals for collaborative research. In the 1995 competition for NIDRR funding, collaborative research proposals were submitted as part of the Model SCI Systems competitive applications. In the 2001 competition, collaborative research was parceled out and a separate competition held. There have been a number of publications stemming from the 1 995 competition; some of the data from these projects are still being explored and used for manuscripts. The outcomes for the 2001 competition will not be known for several years. Collaborative research has the advantage of generating larger numbers more quickly than any 1 center can typically generate, producing a more broadly based sample and, therefore, generalizable result, and facilitating the use of expertise not always available in a single center. Collaborative research activities have been among the most productive aspects of the Model Systems program; the change in the way this component is competed in the most recent competition is yet to be evaluated in terms of its efficacy compared with methods used for funding collaborative research in past competitions.

39 CFR 3020.52 - Supporting justification.

Code of Federal Regulations, 2010 CFR

2010-07-01

...(b), taking into account the factors of 39 U.S.C. 3622(c); (c) Explain why, as to competitive... 39 U.S.C. 3633. (d) Verify that the change does not classify as competitive a product over which the Postal Service exercises sufficient market power that it can, without risk of losing a significant level...

Injuries and Associated Risk Factors Among Adolescent Elite Orienteerers: A 26-Week Prospective Registration Study.

PubMed

von Rosen, Philip; Heijne, Annette I-L M; Frohm, Anna

2016-04-01

In orienteering, the number of injury-registration studies is limited. Most researchers have used a cross-sectional design during specific events and, therefore, have mainly identified acute injuries. To determine the prevalence of injuries by registering acute and overuse injuries in adolescent elite orienteerers over 26 weeks and to study the variation of injury prevalence over the season and the potential risk factors. Cohort study. Two high schools in Sweden with national orienteering teams. All athletes (33 adolescent girls, 31 adolescent boys; age = 17 ± 1 years) from 2 high schools with orienteering teams. We used a weekly Web-based questionnaire to identify the incidence and prevalence of injuries and training variables. Risk factors for injury were calculated using multiple linear regression techniques. The average weekly prevalence of overuse and acute injuries was 35.7% (95% confidence interval = 34.8%, 36.6%) and 1.7% (95% confidence interval = 1.3%, 2.1%), respectively; overuse injuries (78.0%, n = 85) accounted for the majority. The incidence of acute and overuse injuries was highest for the foot/lower leg (48.6%, n = 53), and 71.6% (n = 78) of all injuries affected the foot/lower leg and knee area. Time to the first reported injury was associated with training volume (β = 0.184, P = .001), competition time (β = -0.701, P = .009), running on asphalt roads (β = -0.348, P = .008), and running on forest surfaces and trails (β = -0.331, P = .007), with a model fit of r( 2) = 0.50 (intercept = 2.196, P < .001). During the study, we observed a weekly increase (0.3%) in the prevalence of overuse injuries in the foot/lower leg (r( 2) = 0.33, P = .001); the highest prevalence (26.9%) was at the beginning of the competitive season. Overuse injuries, predominately in the foot/lower leg area, were more common than acute injuries in adolescent elite orienteerers. These injuries had the highest prevalence at the beginning of the competitive season; therefore, this period can be seen as a possible risk factor for sustaining overuse injuries in the foot/lower leg.

Disease management and health care reforms in Germany - does more competition lead to less solidarity?

PubMed

Stock, Stephanie Anja Katharina; Redaelli, Marcus; Lauterbach, Karl Wilhelm

2007-01-01

Up to the 1990s German health care legislation was dominated by measures regulating the supply side. Measures, such as budgets, aimed at volume control and sought to confine the increase of health care spending to the growth of the national income. To curb costs more effectively, competitive elements were introduced in the 1990s with free choice of sickness funds (open enrollment). To balance competition and solidarity, a risk compensation scheme (RCS) was implemented two years prior to open enrollment. Since then, balancing competition and solidarity has been a key feature of all consecutive health care reforms. The implementation of disease management programs in the statutory health insurance (SHI) served the dual purpose to promote quality of care and to foster competition. Preliminary experiences suggest, that the aligning of disease management programs with a RCS can greatly aid its implementation and benefit solidarity and competition.

Project safety as a sustainable competitive advantage.

PubMed

Rechenthin, David

2004-01-01

To be consistently profitable, a construction company must complete projects in scope, on schedule, and on budget. At the same time, the nature of the often high-risk work performed by construction companies can result in high accident rates. Clients and other stakeholders are placing increasing pressure on companies to decrease those accident rates. Clients routinely demand copies of safety plans and evidence of past results at the "pre-qualification" or "request for proposal" stages of the procurement process. Are high accident rates and the associated costs just a part of business? Companies that deliver on scope, schedule, and budget have a competitive advantage. Is it possible for projects with low accident rates to use it as a competitive advantage? Is the value added by safety just a temporary or parity issue, or does a successful safety program offer significant advantage to the company and the client? This article concludes that in the case of a high-risk industry, such as the construction industry, an organization with a successful safety program can promote safety performance as a sustainable competitive advantage. It is a choice the company can make.

The Effects of Level of Competition, Sport, and Sex on the Incidence of First-Time Noncontact Anterior Cruciate Ligament Injury.

PubMed

Beynnon, Bruce D; Vacek, Pamela M; Newell, Maira K; Tourville, Timothy W; Smith, Helen C; Shultz, Sandra J; Slauterbeck, James R; Johnson, Robert J

2014-08-01

Anterior cruciate ligament (ACL) injuries are disabling and are associated with the early onset of posttraumatic osteoarthritis. Little is known regarding the incidence rate of first-time noncontact ACL injuries sustained during athletic events and how they are independently influenced by level of competition, type of sport, and the participant's sex. Level of competition (college or high school), type of sport (soccer, basketball, lacrosse, field hockey, football, rugby, volleyball), and the athlete's sex independently influence the incidence rate of first-time noncontact ACL injuries. Cohort study; Level of evidence, 2. Between fall 2008 and spring 2012, first-time noncontact ACL injury data were collected from 8 colleges and 18 high schools across 7 sports. Athlete exposure was computed retrospectively using team rosters and numbers of scheduled practices and games. Injury incidence rates (IRs) were computed per 1000 athlete exposures. The independent effects of level of competition, sport, and sex on ACL injury risk were estimated by Poisson regression. Colleges reported 48 ACL injuries with 320,719 athlete exposures across all sports studied (IR = 0.150 per 1000 person-days), while high schools reported 53 injuries with 873,057 athlete exposures (IR = 0.061). After adjustment for differences in sport and sex, college athletes had a significantly higher injury risk than did high school athletes (adjusted relative risk [RR], 2.38; 95% CI, 1.55-3.54). The overall IR for female athletes was 0.112 compared with 0.063 for males. After adjustment for sport and level of play, females were more than twice as likely to have a first-time ACL injury compared with males (RR, 2.10; 95% CI, 1.34-3.27). With lacrosse as the reference group, risk of first-time noncontact ACL injury was significantly higher for soccer players (RR, 1.77) and for rugby players (RR, 2.23), independent of level of play and sex. An athlete's risk of having a first-time noncontact ACL injury is independently influenced by level of competition, the participant's sex, and type of sport, and there are no interactions between their effects. Female college athletes have the highest risk of having a first-time noncontact ACL injury among the groups studied. © 2014 The Author(s).

Competitive market for multiple firms and economic crisis

NASA Astrophysics Data System (ADS)

Tao, Yong

2010-09-01

The origin of economic crises is a key problem for economics. We present a model of long-run competitive markets to show that the multiplicity of behaviors in an economic system, over a long time scale, emerge as statistical regularities (perfectly competitive markets obey Bose-Einstein statistics and purely monopolistic-competitive markets obey Boltzmann statistics) and that how interaction among firms influences the evolutionary of competitive markets. It has been widely accepted that perfect competition is most efficient. Our study shows that the perfectly competitive system, as an extreme case of competitive markets, is most efficient but not stable, and gives rise to economic crises as society reaches full employment. In the economic crisis revealed by our model, many firms condense (collapse) into the lowest supply level (zero supply, namely, bankruptcy status), in analogy to Bose-Einstein condensation. This curious phenomenon arises because perfect competition (homogeneous competitions) equals symmetric (indistinguishable) investment direction, a fact abhorred by nature. Therefore, we urge the promotion of monopolistic competition (heterogeneous competitions) rather than perfect competition. To provide early warning of economic crises, we introduce a resolving index of investment, which approaches zero in the run-up to an economic crisis. On the other hand, our model discloses, as a profound conclusion, that the technological level for a long-run social or economic system is proportional to the freedom (disorder) of this system; in other words, technology equals the entropy of system. As an application of this concept, we give a possible answer to the Needham question: “Why was it that despite the immense achievements of traditional China it had been in Europe and not in China that the scientific and industrial revolutions occurred?”

Competitive market for multiple firms and economic crisis.

PubMed

Tao, Yong

2010-09-01

The origin of economic crises is a key problem for economics. We present a model of long-run competitive markets to show that the multiplicity of behaviors in an economic system, over a long time scale, emerge as statistical regularities (perfectly competitive markets obey Bose-Einstein statistics and purely monopolistic-competitive markets obey Boltzmann statistics) and that how interaction among firms influences the evolutionary of competitive markets. It has been widely accepted that perfect competition is most efficient. Our study shows that the perfectly competitive system, as an extreme case of competitive markets, is most efficient but not stable, and gives rise to economic crises as society reaches full employment. In the economic crisis revealed by our model, many firms condense (collapse) into the lowest supply level (zero supply, namely, bankruptcy status), in analogy to Bose-Einstein condensation. This curious phenomenon arises because perfect competition (homogeneous competitions) equals symmetric (indistinguishable) investment direction, a fact abhorred by nature. Therefore, we urge the promotion of monopolistic competition (heterogeneous competitions) rather than perfect competition. To provide early warning of economic crises, we introduce a resolving index of investment, which approaches zero in the run-up to an economic crisis. On the other hand, our model discloses, as a profound conclusion, that the technological level for a long-run social or economic system is proportional to the freedom (disorder) of this system; in other words, technology equals the entropy of system. As an application of this concept, we give a possible answer to the Needham question: "Why was it that despite the immense achievements of traditional China it had been in Europe and not in China that the scientific and industrial revolutions occurred?"

Is healthy competition healthy? New evidence of the impact of hospital competition.

PubMed

Gift, Thomas L; Arnould, Richard; DeBrock, Larry

2002-01-01

Competition among hospitals is commonly regarded as inefficient due to the medical arms race phenomenon, but most evidence for this hypothesis predates the Medicare prospective payment system and preferred provider legislation. Recent studies indicate hospital competition reduces costs and prices, but nearly all such research has focused on California. We add to the body of literature that analyzes the effects of competition in hospital markets. Using data from the state of Washington, we show that hospitals assume more risk in competitive markets by being more likely to accept prospective payment arrangements with insurers. If the arrangement is retrospective, the hospital is more likely to offer a discount as the number of competing hospitals increases. Both findings indicate that competitive forces operate the same in hospital markets as in most others: as the number of competitors increases, prices decrease and market power shifts from the suppliers to purchasers. The medical arms race hypothesis that favors more concentrated hospital markets no longer appears to be valid.

Analysis of inter-country input-output table based on citation network: How to measure the competition and collaboration between industrial sectors on the global value chain

PubMed Central

2017-01-01

The input-output table is comprehensive and detailed in describing the national economic system with complex economic relationships, which embodies information of supply and demand among industrial sectors. This paper aims to scale the degree of competition/collaboration on the global value chain from the perspective of econophysics. Global Industrial Strongest Relevant Network models were established by extracting the strongest and most immediate industrial relevance in the global economic system with inter-country input-output tables and then transformed into Global Industrial Resource Competition Network/Global Industrial Production Collaboration Network models embodying the competitive/collaborative relationships based on bibliographic coupling/co-citation approach. Three indicators well suited for these two kinds of weighted and non-directed networks with self-loops were introduced, including unit weight for competitive/collaborative power, disparity in the weight for competitive/collaborative amplitude and weighted clustering coefficient for competitive/collaborative intensity. Finally, these models and indicators were further applied to empirically analyze the function of sectors in the latest World Input-Output Database, to reveal inter-sector competitive/collaborative status during the economic globalization. PMID:28873432

Analysis of inter-country input-output table based on citation network: How to measure the competition and collaboration between industrial sectors on the global value chain.

PubMed

Xing, Lizhi

2017-01-01

The input-output table is comprehensive and detailed in describing the national economic system with complex economic relationships, which embodies information of supply and demand among industrial sectors. This paper aims to scale the degree of competition/collaboration on the global value chain from the perspective of econophysics. Global Industrial Strongest Relevant Network models were established by extracting the strongest and most immediate industrial relevance in the global economic system with inter-country input-output tables and then transformed into Global Industrial Resource Competition Network/Global Industrial Production Collaboration Network models embodying the competitive/collaborative relationships based on bibliographic coupling/co-citation approach. Three indicators well suited for these two kinds of weighted and non-directed networks with self-loops were introduced, including unit weight for competitive/collaborative power, disparity in the weight for competitive/collaborative amplitude and weighted clustering coefficient for competitive/collaborative intensity. Finally, these models and indicators were further applied to empirically analyze the function of sectors in the latest World Input-Output Database, to reveal inter-sector competitive/collaborative status during the economic globalization.

A new theory of plant-microbe nutrient competition resolves inconsistencies between observations and model predictions.

PubMed

Zhu, Qing; Riley, William J; Tang, Jinyun

2017-04-01

Terrestrial plants assimilate anthropogenic CO 2 through photosynthesis and synthesizing new tissues. However, sustaining these processes requires plants to compete with microbes for soil nutrients, which therefore calls for an appropriate understanding and modeling of nutrient competition mechanisms in Earth System Models (ESMs). Here, we survey existing plant-microbe competition theories and their implementations in ESMs. We found no consensus regarding the representation of nutrient competition and that observational and theoretical support for current implementations are weak. To reconcile this situation, we applied the Equilibrium Chemistry Approximation (ECA) theory to plant-microbe nitrogen competition in a detailed grassland 15 N tracer study and found that competition theories in current ESMs fail to capture observed patterns and the ECA prediction simplifies the complex nature of nutrient competition and quantitatively matches the 15 N observations. Since plant carbon dynamics are strongly modulated by soil nutrient acquisition, we conclude that (1) predicted nutrient limitation effects on terrestrial carbon accumulation by existing ESMs may be biased and (2) our ECA-based approach may improve predictions by mechanistically representing plant-microbe nutrient competition. © 2016 by the Ecological Society of America.

Affordable Care Act risk adjustment: overview, context, and challenges.

PubMed

Kautter, John; Pope, Gregory C; Keenan, Patricia

2014-01-01

Beginning in 2014, individuals and small businesses will be able to purchase private health insurance through competitive marketplaces. The Affordable Care Act (ACA) provides for a program of risk adjustment in the individual and small group markets in 2014 as Marketplaces are implemented and new market reforms take effect. The purpose of risk adjustment is to lessen or eliminate the influence of risk selection on the premiums that plans charge and the incentive for plans to avoid sicker enrollees. This article--the first of three in the Medicare & Medicaid Research Review--describes the key program goal and issues in the Department of Health and Human Services (HHS) developed risk adjustment methodology, and identifies key choices in how the methodology responds to these issues. The goal of the HHS risk adjustment methodology is to compensate health insurance plans for differences in enrollee health mix so that plan premiums reflect differences in scope of coverage and other plan factors, but not differences in health status. The methodology includes a risk adjustment model and a risk transfer formula that together address this program goal as well as three issues specific to ACA risk adjustment: 1) new population; 2) cost and rating factors; and 3) balanced transfers within state/market. The risk adjustment model, described in the second article, estimates differences in health risks taking into account the new population and scope of coverage (actuarial value level). The transfer formula, described in the third article, calculates balanced transfers that are intended to account for health risk differences while preserving permissible premium differences.

Sperm midpiece length predicts sperm swimming velocity in house mice.

PubMed

Firman, Renée C; Simmons, Leigh W

2010-08-23

Evolutionary biologists have argued that there should be a positive relationship between sperm size and sperm velocity, and that these traits influence a male's sperm competitiveness. However, comparative analyses investigating the evolutionary associations between sperm competition risk and sperm morphology have reported inconsistent patterns of association, and in vitro sperm competition experiments have further confused the issue; in some species, males with longer sperm achieve more competitive fertilization, while in other species males with shorter sperm have greater sperm competitiveness. Few investigations have attempted to address this problem. Here, we investigated the relationship between sperm morphology and sperm velocity in house mice (Mus domesticus). We conducted in vitro sperm velocity assays on males from established selection lines, and found that sperm midpiece size was the only phenotypic predictor of sperm swimming velocity.

Coupled Inverted Pendula Model of Competition and Cooperation

NASA Astrophysics Data System (ADS)

Yoshida, Katsutoshi; Ohta, Hiroki

A coupled inverted pendula model of competition and cooperation is proposed to develop a purely mechanical implementation comparable to the Lotka-Volterra competition model. It is shown numerically that the proposed model can produce the four stable equilibriums analogous to ecological coexistence, two states of dominance, and scramble. The authors also propose two types of open-loop strategies to switch the equilibriums. The proposed strategies can be associated with an attack and a counter attack of agents through a metaphor of martial arts.

Estimating the Effect of Competition on Trait Evolution Using Maximum Likelihood Inference.

PubMed

Drury, Jonathan; Clavel, Julien; Manceau, Marc; Morlon, Hélène

2016-07-01

Many classical ecological and evolutionary theoretical frameworks posit that competition between species is an important selective force. For example, in adaptive radiations, resource competition between evolving lineages plays a role in driving phenotypic diversification and exploration of novel ecological space. Nevertheless, current models of trait evolution fit to phylogenies and comparative data sets are not designed to incorporate the effect of competition. The most advanced models in this direction are diversity-dependent models where evolutionary rates depend on lineage diversity. However, these models still treat changes in traits in one branch as independent of the value of traits on other branches, thus ignoring the effect of species similarity on trait evolution. Here, we consider a model where the evolutionary dynamics of traits involved in interspecific interactions are influenced by species similarity in trait values and where we can specify which lineages are in sympatry. We develop a maximum likelihood based approach to fit this model to combined phylogenetic and phenotypic data. Using simulations, we demonstrate that the approach accurately estimates the simulated parameter values across a broad range of parameter space. Additionally, we develop tools for specifying the biogeographic context in which trait evolution occurs. In order to compare models, we also apply these biogeographic methods to specify which lineages interact sympatrically for two diversity-dependent models. Finally, we fit these various models to morphological data from a classical adaptive radiation (Greater Antillean Anolis lizards). We show that models that account for competition and geography perform better than other models. The matching competition model is an important new tool for studying the influence of interspecific interactions, in particular competition, on phenotypic evolution. More generally, it constitutes a step toward a better integration of interspecific interactions in many ecological and evolutionary processes. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Individualism in plant populations: using stochastic differential equations to model individual neighbourhood-dependent plant growth.

PubMed

Lv, Qiming; Schneider, Manuel K; Pitchford, Jonathan W

2008-08-01

We study individual plant growth and size hierarchy formation in an experimental population of Arabidopsis thaliana, within an integrated analysis that explicitly accounts for size-dependent growth, size- and space-dependent competition, and environmental stochasticity. It is shown that a Gompertz-type stochastic differential equation (SDE) model, involving asymmetric competition kernels and a stochastic term which decreases with the logarithm of plant weight, efficiently describes individual plant growth, competition, and variability in the studied population. The model is evaluated within a Bayesian framework and compared to its deterministic counterpart, and to several simplified stochastic models, using distributional validation. We show that stochasticity is an important determinant of size hierarchy and that SDE models outperform the deterministic model if and only if structural components of competition (asymmetry; size- and space-dependence) are accounted for. Implications of these results are discussed in the context of plant ecology and in more general modelling situations.

78 FR 29157 - Certain Digital Models, Digital Data, and Treatment Plans for Use, in Making Incremental Dental...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-17

... INTERNATIONAL TRADE COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use... conditions in the United States economy, the production of like or directly competitive articles in the..., competitive conditions in the United States economy, the production of like or directly competitive articles...

Charter School Competition, Organization, and Achievement in Traditional Public Schools

ERIC Educational Resources Information Center

Davis, Tomeka M.

2013-01-01

Market models of education reform predict that the growth of charter schools will infuse competition into the public school sector, forcing traditional public schools to improve the practices they engage in to educate students. Some scholars have criticized these models, arguing that competition from charter schools is unlikely to produce…

Lexical Selection Is Competitive: Evidence from Indirectly Activated Semantic Associates during Picture Naming

ERIC Educational Resources Information Center

Melinger, Alissa; Rahman, Rasha Abdel

2013-01-01

In this study, we present 3 picture-word interference (PWI) experiments designed to investigate whether lexical selection processes are competitive. We focus on semantic associative relations, which should interfere according to competitive models but not according to certain noncompetitive models. In a modified version of the PWI paradigm,…

Evolving Nutritional Strategies in the Presence of Competition: A Geometric Agent-Based Model

PubMed Central

Senior, Alistair M.; Charleston, Michael A.; Lihoreau, Mathieu; Buhl, Jerome; Raubenheimer, David; Simpson, Stephen J.

2015-01-01

Access to nutrients is a key factor governing development, reproduction and ultimately fitness. Within social groups, contest-competition can fundamentally affect nutrient access, potentially leading to reproductive asymmetry among individuals. Previously, agent-based models have been combined with the Geometric Framework of nutrition to provide insight into how nutrition and social interactions affect one another. Here, we expand this modelling approach by incorporating evolutionary algorithms to explore how contest-competition over nutrient acquisition might affect the evolution of animal nutritional strategies. Specifically, we model tolerance of nutrient excesses and deficits when ingesting nutritionally imbalanced foods, which we term ‘nutritional latitude’; a higher degree of nutritional latitude constitutes a higher tolerance of nutritional excess and deficit. Our results indicate that a transition between two alternative strategies occurs at moderate to high levels of competition. When competition is low, individuals display a low level of nutritional latitude and regularly switch foods in search of an optimum. When food is scarce and contest-competition is intense, high nutritional latitude appears optimal, and individuals continue to consume an imbalanced food for longer periods before attempting to switch to an alternative. However, the relative balance of nutrients within available foods also strongly influences at what levels of competition, if any, transitions between these two strategies occur. Our models imply that competition combined with reproductive skew in social groups can play a role in the evolution of diet breadth. We discuss how the integration of agent-based, nutritional and evolutionary modelling may be applied in future studies to further understand the evolution of nutritional strategies across social and ecological contexts. PMID:25815976

A random-censoring Poisson model for underreported data.

PubMed

de Oliveira, Guilherme Lopes; Loschi, Rosangela Helena; Assunção, Renato Martins

2017-12-30

A major challenge when monitoring risks in socially deprived areas of under developed countries is that economic, epidemiological, and social data are typically underreported. Thus, statistical models that do not take the data quality into account will produce biased estimates. To deal with this problem, counts in suspected regions are usually approached as censored information. The censored Poisson model can be considered, but all censored regions must be precisely known a priori, which is not a reasonable assumption in most practical situations. We introduce the random-censoring Poisson model (RCPM) which accounts for the uncertainty about both the count and the data reporting processes. Consequently, for each region, we will be able to estimate the relative risk for the event of interest as well as the censoring probability. To facilitate the posterior sampling process, we propose a Markov chain Monte Carlo scheme based on the data augmentation technique. We run a simulation study comparing the proposed RCPM with 2 competitive models. Different scenarios are considered. RCPM and censored Poisson model are applied to account for potential underreporting of early neonatal mortality counts in regions of Minas Gerais State, Brazil, where data quality is known to be poor. Copyright © 2017 John Wiley & Sons, Ltd.

Chemosensory assessment of sperm competition levels and the evolution of internal spermatophore guarding

PubMed Central

Carazo, P; Font, E; Alfthan, B

2006-01-01

Males of many species adjust their reproductive behaviour according to the perceived risk of sperm competition. Although this phenomenon is widespread in insects and other animals, the mechanisms that allow mates to assess sperm competition levels remain largely unexplored. In this study, we analysed the mating behaviour of pairs of Tenebrio molitor beetles under three odour treatments representing increasing levels of sperm competition risk (SCR) and sperm competition intensity (SCI). Copula duration and male and female post-copulatory behaviour varied significantly with odour treatment. Both copula duration and post-copulatory associations (PCAs) increased significantly in odour treatments reflecting high male density. To our knowledge, this is the first study to report that insects may assess the actual density of potential competitors at the time of mating, a cue to SCR and SCI, on the basis of chemical cues. In T. molitor, males inhibit sperm release from the spermatophore of a rival male when remating takes place at short intervals. We show that, when sperm competition levels are high, PCAs increase female remating interval just above that necessary to prevent spermatophore inhibition by rival males. This finding strongly suggests that strategic male behaviour plays a ‘spermatophore guarding’ role in this species. Although common in insects with external spermatophore transfer, spermatophore guarding is not expected in species with rapid ejaculate transfer and internal spermatophore delivery. Our results reveal that spermatophore guarding may evolve, even under these circumstances, as an evolutionary response to short-term spermatophore inhibition or displacement mechanisms. PMID:17148255

[Nursing care during sporting competitions, an on-site first aid kit].

PubMed

Fernández García, Julián

2008-12-01

In the world of sports, just as in daily life, many situations can bring with them some kind of risk to our physical integrity If we add on the additional factor competition against an adversary and against oneself bears, this risk multiplies and numerous emergency situations arise; these risks may be sporting in nature or even vital to survival. There are various professional figures inside and outside sports capable to deal with an emergency, but the nursing professional is best positioned to provide all the care an athlete needs. Furthermore, when one adds on the specific knowledge belonging to sports and the required materials, a nurse who specializes in sports medicine becomes the most complete medical professional to care for an athlete.

Space Launch System (SLS) Program Overview NASA Research Announcement (NRA) Advanced Booster (AB) Engineering Demonstration and Risk Reduction (EDRR) Industry Day

NASA Technical Reports Server (NTRS)

May, Todd A.

2011-01-01

SLS is a national capability that empowers entirely new exploration for missions of national importance. Program key tenets are safety, affordability, and sustainability. SLS builds on a solid foundation of experience and current capacities to enable a timely initial capability and evolve to a flexible heavy-lift capability through competitive opportunities: (1) Reduce risks leading to an affordable Advanced Booster that meets the evolved capabilities of SLS (2) Enable competition by mitigating targeted Advanced Booster risks to enhance SLS affordability and performance The road ahead promises to be an exciting journey for present and future generations, and we look forward to working with you to continue America fs space exploration.

Analysis of inter-country input-output table based on bibliographic coupling network: How industrial sectors on the GVC compete for production resources

NASA Astrophysics Data System (ADS)

Guan, Jun; Xu, Xiaoyu; Xing, Lizhi

2018-03-01

The input-output table is comprehensive and detailed in describing national economic systems with abundance of economic relationships depicting information of supply and demand among industrial sectors. This paper focuses on how to quantify the degree of competition on the global value chain (GVC) from the perspective of econophysics. Global Industrial Strongest Relevant Network models are established by extracting the strongest and most immediate industrial relevance in the global economic system with inter-country input-output (ICIO) tables and then have them transformed into Global Industrial Resource Competition Network models to analyze the competitive relationships based on bibliographic coupling approach. Three indicators well suited for the weighted and undirected networks with self-loops are introduced here, including unit weight for competitive power, disparity in the weight for competitive amplitude and weighted clustering coefficient for competitive intensity. Finally, these models and indicators were further applied empirically to analyze the function of industrial sectors on the basis of the latest World Input-Output Database (WIOD) in order to reveal inter-sector competitive status during the economic globalization.

Network Reputational Risks of the Educational Institution

ERIC Educational Resources Information Center

Bekturganov, Zakir Z.

2016-01-01

Development of the global information space is the basis of change in the educational paradigm and the formation of the world market of educational services. Traditional educational institutions face new challenges and risks that undermine their competitiveness. This implies the emerging phenomenon of online reputation risks, with significant…

Optimal stomatal behavior with competition for water and risk of hydraulic impairment.

PubMed

Wolf, Adam; Anderegg, William R L; Pacala, Stephen W

2016-11-15

For over 40 y the dominant theory of stomatal behavior has been that plants should open stomates until the carbon gained by an infinitesimal additional opening balances the additional water lost times a water price that is constant at least over short periods. This theory has persisted because of its remarkable success in explaining strongly supported simple empirical models of stomatal conductance, even though we have also known for over 40 y that the theory is not consistent with competition among plants for water. We develop an alternative theory in which plants maximize carbon gain without pricing water loss and also add two features to both this and the classical theory, which are strongly supported by empirical evidence: (i) water flow through xylem that is progressively impaired as xylem water potential drops and (ii) fitness or carbon costs associated with low water potentials caused by a variety of mechanisms, including xylem damage repair. We show that our alternative carbon-maximization optimization is consistent with plant competition because it yields an evolutionary stable strategy (ESS)-species with the ESS stomatal behavior that will outcompete all others. We further show that, like the classical theory, the alternative theory also explains the functional forms of empirical stomatal models. We derive ways to test between the alternative optimization criteria by introducing a metric-the marginal xylem tension efficiency, which quantifies the amount of photosynthesis a plant will forego from opening stomatal an infinitesimal amount more to avoid a drop in water potential.

Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect

PubMed Central

Strengbom, Joachim; Viketoft, Maria; Bommarco, Riccardo

2016-01-01

Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition: Dactylis glomerata L., which is competitively favoured by nitrogen addition, and Festuca rubra L., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage of D. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage of F. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability of F. rubra, and a 23% increase in that of D. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory. D. glomerata remained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion of F. rubra. Belowground herbivory appeared to mitigate the influence of aboveground herbivory, and this mechanism may play a role for plant species coexistence. PMID:27069805

Aboveground insect herbivory increases plant competitive asymmetry, while belowground herbivory mitigates the effect.

PubMed

Borgström, Pernilla; Strengbom, Joachim; Viketoft, Maria; Bommarco, Riccardo

2016-01-01

Insect herbivores can shift the composition of a plant community, but the mechanism underlying such shifts remains largely unexplored. A possibility is that insects alter the competitive symmetry between plant species. The effect of herbivory on competition likely depends on whether the plants are subjected to aboveground or belowground herbivory or both, and also depends on soil nitrogen levels. It is unclear how these biotic and abiotic factors interactively affect competition. In a greenhouse experiment, we measured competition between two coexisting grass species that respond differently to nitrogen deposition: Dactylis glomerata L., which is competitively favoured by nitrogen addition, and Festuca rubra L., which is competitively favoured on nitrogen-poor soils. We predicted: (1) that aboveground herbivory would reduce competitive asymmetry at high soil nitrogen by reducing the competitive advantage of D. glomerata; and (2), that belowground herbivory would relax competition at low soil nitrogen, by reducing the competitive advantage of F. rubra. Aboveground herbivory caused a 46% decrease in the competitive ability of F. rubra, and a 23% increase in that of D. glomerata, thus increasing competitive asymmetry, independently of soil nitrogen level. Belowground herbivory did not affect competitive symmetry, but the combined influence of above- and belowground herbivory was weaker than predicted from their individual effects. Belowground herbivory thus mitigated the increased competitive asymmetry caused by aboveground herbivory. D. glomerata remained competitively dominant after the cessation of aboveground herbivory, showing that the influence of herbivory continued beyond the feeding period. We showed that insect herbivory can strongly influence plant competitive interactions. In our experimental plant community, aboveground insect herbivory increased the risk of competitive exclusion of F. rubra. Belowground herbivory appeared to mitigate the influence of aboveground herbivory, and this mechanism may play a role for plant species coexistence.

A game-based decision support methodology for competitive systems design

NASA Astrophysics Data System (ADS)

Briceno, Simon Ignacio

This dissertation describes the development of a game-based methodology that facilitates the exploration and selection of research and development (R&D) projects under uncertain competitive scenarios. The proposed method provides an approach that analyzes competitor positioning and formulates response strategies to forecast the impact of technical design choices on a project's market performance. A critical decision in the conceptual design phase of propulsion systems is the selection of the best architecture, centerline, core size, and technology portfolio. This selection can be challenging when considering evolving requirements from both the airframe manufacturing company and the airlines in the market. Furthermore, the exceedingly high cost of core architecture development and its associated risk makes this strategic architecture decision the most important one for an engine company. Traditional conceptual design processes emphasize performance and affordability as their main objectives. These areas alone however, do not provide decision-makers with enough information as to how successful their engine will be in a competitive market. A key objective of this research is to examine how firm characteristics such as their relative differences in completing R&D projects, differences in the degree of substitutability between different project types, and first/second-mover advantages affect their product development strategies. Several quantitative methods are investigated that analyze business and engineering strategies concurrently. In particular, formulations based on the well-established mathematical field of game theory are introduced to obtain insights into the project selection problem. The use of game theory is explored in this research as a method to assist the selection process of R&D projects in the presence of imperfect market information. The proposed methodology focuses on two influential factors: the schedule uncertainty of project completion times and the uncertainty associated with competitive reactions. A normal-form matrix is created to enumerate players, their moves and payoffs, and to formulate a process by which an optimal decision can be achieved. The non-cooperative model is tested using the concept of a Nash equilibrium to identify potential strategies that are robust to uncertain market fluctuations (e.g: uncertainty in airline demand, airframe requirements and competitor positioning). A first/second-mover advantage parameter is used as a scenario dial to adjust market rewards and firms' payoffs. The methodology is applied to a commercial aircraft engine selection study where engine firms must select an optimal engine project for development. An engine modeling and simulation framework is developed to generate a broad engine project portfolio. The creation of a customer value model enables designers to incorporate airline operation characteristics into the engine modeling and simulation process to improve the accuracy of engine/customer matching. Summary. Several key findings are made that provide recommendations on project selection strategies for firms uncertain as to when they will enter the market. The proposed study demonstrates that within a technical design environment, a rational and analytical means of modeling project development strategies is beneficial in high market risk situations.

Life history trade-off moderates model predictions of diversity loss from climate change

PubMed Central

2017-01-01

Climate change can trigger species range shifts, local extinctions and changes in diversity. Species interactions and dispersal capacity are important mediators of community responses to climate change. The interaction between multispecies competition and variation in dispersal capacity has recently been shown to exacerbate the effects of climate change on diversity and to increase predictions of extinction risk dramatically. Dispersal capacity, however, is part of a species’ overall ecological strategy and are likely to trade off with other aspects of its life history that influence population growth and persistence. In plants, a well-known example is the trade-off between seed mass and seed number. The presence of such a trade-off might buffer the diversity loss predicted by models with random but neutral (i.e. not impacting fitness otherwise) differences in dispersal capacity. Using a trait-based metacommunity model along a warming climatic gradient the effect of three different dispersal scenarios on model predictions of diversity change were compared. Adding random variation in species dispersal capacity caused extinctions by the introduction of strong fitness differences due an inherent property of the dispersal kernel. Simulations including a fitness-equalising trade-off based on empirical relationships between seed mass (here affecting dispersal distance, establishment probability, and seedling biomass) and seed number (fecundity) maintained higher initial species diversity and predicted lower extinction risk and diversity loss during climate change than simulations with variable dispersal capacity. Large seeded species persisted during climate change, but developed lags behind their climate niche that may cause extinction debts. Small seeded species were more extinction-prone during climate change but tracked their niches through dispersal and colonisation, despite competitive resistance from residents. Life history trade-offs involved in coexistence mechanisms may increase community resilience to future climate change and are useful guides for model development. PMID:28520770

Biodiversity Can Help Prevent Malaria Outbreaks in Tropical Forests

PubMed Central

Laporta, Gabriel Zorello; de Prado, Paulo Inácio Knegt Lopez; Kraenkel, Roberto André; Coutinho, Renato Mendes; Sallum, Maria Anice Mureb

2013-01-01

Background Plasmodium vivax is a widely distributed, neglected parasite that can cause malaria and death in tropical areas. It is associated with an estimated 80–300 million cases of malaria worldwide. Brazilian tropical rain forests encompass host- and vector-rich communities, in which two hypothetical mechanisms could play a role in the dynamics of malaria transmission. The first mechanism is the dilution effect caused by presence of wild warm-blooded animals, which can act as dead-end hosts to Plasmodium parasites. The second is diffuse mosquito vector competition, in which vector and non-vector mosquito species compete for blood feeding upon a defensive host. Considering that the World Health Organization Malaria Eradication Research Agenda calls for novel strategies to eliminate malaria transmission locally, we used mathematical modeling to assess those two mechanisms in a pristine tropical rain forest, where the primary vector is present but malaria is absent. Methodology/Principal Findings The Ross–Macdonald model and a biodiversity-oriented model were parameterized using newly collected data and data from the literature. The basic reproduction number () estimated employing Ross–Macdonald model indicated that malaria cases occur in the study location. However, no malaria cases have been reported since 1980. In contrast, the biodiversity-oriented model corroborated the absence of malaria transmission. In addition, the diffuse competition mechanism was negatively correlated with the risk of malaria transmission, which suggests a protective effect provided by the forest ecosystem. There is a non-linear, unimodal correlation between the mechanism of dead-end transmission of parasites and the risk of malaria transmission, suggesting a protective effect only under certain circumstances (e.g., a high abundance of wild warm-blooded animals). Conclusions/Significance To achieve biological conservation and to eliminate Plasmodium parasites in human populations, the World Health Organization Malaria Eradication Research Agenda should take biodiversity issues into consideration. PMID:23556023

A Canopy Architectural Model to Study the Competitive Ability of Chickpea with Sowthistle

PubMed Central

Cici, S-Zahra-Hosseini; Adkins, Steve; Hanan, Jim

2008-01-01

Background and Aims Improving the competitive ability of crops is a sustainable method of weed management. This paper shows how a virtual plant model of competition between chickpea (Cicer arietinum) and sowthistle (Sonchus oleraceus) can be used as a framework for discovering and/or developing more competitive chickpea cultivars. Methods The virtual plant models were developed using the L-systems formalism, parameterized according to measurements taken on plants at intervals during their development. A quasi-Monte Carlo light-environment model was used to model the effect of chickpea canopy on the development of sowthistle. The chickpea–light environment–sowthistle model (CLES model) captured the hypothesis that the architecture of chickpea plants modifies the light environment inside the canopy and determines sowthistle growth and development pattern. The resulting CLES model was parameterized for different chickpea cultivars (viz. ‘Macarena’, ‘Bumper’, ‘Jimbour’ and ‘99071-1001’) to compare their competitive ability with sowthistle. To validate the CLES model, an experiment was conducted using the same four chickpea cultivars as different treatments with a sowthistle growing under their canopy. Results and Conclusions The growth of sowthistle, both in silico and in glasshouse experiments, was reduced most by ‘99071-1001’, a cultivar with a short phyllochron. The second rank of competitive ability belonged to ‘Macarena’ and ‘Bumper’, while ‘Jimbour’ was the least competitive cultivar. The architecture of virtual chickpea plants modified the light inside the canopy, which influenced the growth and development of the sowthistle plants in response to different cultivars. This is the first time that a virtual plant model of a crop–weed interaction has been developed. This virtual plant model can serve as a platform for a broad range of applications in the study of chickpea–weed interactions and their environment. PMID:18375962

Plant water use affects competition for nitrogen: why drought favors invasive species in California.

PubMed

Everard, Katherine; Seabloom, Eric W; Harpole, W Stanley; de Mazancourt, Claire

2010-01-01

Abstract: Classic resource competition theory typically treats resource supply rates as independent; however, nutrient supplies can be affected by plants indirectly, with important consequences for model predictions. We demonstrate this general phenomenon by using a model in which competition for nitrogen is mediated by soil moisture, with competitive outcomes including coexistence and multiple stable states as well as competitive exclusion. In the model, soil moisture regulates nitrogen availability through soil moisture dependence of microbial processes, leaching, and plant uptake. By affecting water availability, plants also indirectly affect nitrogen availability and may therefore alter the competitive outcome. Exotic annual species from the Mediterranean have displaced much of the native perennial grasses in California. Nitrogen and water have been shown to be potentially limiting in this system. We parameterize the model for a Californian grassland and show that soil moisture-mediated competition for nitrogen can explain the annual species' dominance in drier areas, with coexistence expected in wetter regions. These results are concordant with larger biogeographic patterns of grassland invasion in the Pacific states of the United States, in which annual grasses have invaded most of the hot, dry grasslands in California but perennial grasses dominate the moister prairies of northern California, Oregon, and Washington.

An empirical and model study on automobile market in Taiwan

NASA Astrophysics Data System (ADS)

Tang, Ji-Ying; Qiu, Rong; Zhou, Yueping; He, Da-Ren

2006-03-01

We have done an empirical investigation on automobile market in Taiwan including the development of the possession rate of the companies in the market from 1979 to 2003, the development of the largest possession rate, and so on. A dynamic model for describing the competition between the companies is suggested based on the empirical study. In the model each company is given a long-term competition factor (such as technology, capital and scale) and a short-term competition factor (such as management, service and advertisement). Then the companies play games in order to obtain more possession rate in the market under certain rules. Numerical simulation based on the model display a competition developing process, which qualitatively and quantitatively agree with our empirical investigation results.

From which level of competition in clubs are adolescents at greater risk of injury compared with outside-of-clubs athletes? A school-based study.

PubMed

Luiggi, Maxime; Rindler, Victoria; Griffet, Jean

2018-02-01

Sport practice is a key factor in a person's physical and mental health but, for adolescent athletes, some injuries lead to health problems in the long term. The literature provides multiple factors for understanding injury but does not give information about injury risk related to each level of play in a large sample of multisport athletes. This study investigates this relationship in 14- to 19-year-old adolescents. The survey on adolescents and health was conducted in classrooms of France, from February to March 2015. Only sports players were included in the analyses (n = 986). The levels of play were divided into five categories: outside of a club/no competition, club player/no competition, club player/local level, club player/state level and club player/national and higher level. A three-step binary logistic regression analysis with age, sex, type of sport, weekly hours of exposure, and level of play was used. During the past year, 48.1% of the adolescents were injured. Age and sex were not risk factors. The injury risk associated with the increases in level of play is higher than those related to the hours of exposure per week or the type of sport. In clubs, adolescents who do not compete or play at a local level showed no evidence of greater injury risk whereas state-level and national- and higher-level athletes were at greater risk than outside-of-club players (OR = 2.18, 95%CI = 1.13-3.94 and OR = 3.89, 95%CI = 2.07-7.31, respectively). Adolescents who play sports in clubs are clearly more exposed to injury than those who play outside of a club, mainly from state level. Age and sex are not related to injury. Future epidemiological studies should control adolescents' level of play. Special attention should be accorded to the injury risk of athletes playing at these levels of competition.

Market structure and the role of consumer information in the physician services industry: an empirical test.

PubMed

Wong, H S

1996-04-01

This paper applies Panzar and Rosse's (1987) econometric test of market structure to examine two long-debated issues: What is the market structure for physician services? Do more physicians in a market area raise the search cost of obtaining consumer information and increase prices (Satterthwaite, 1979, 1985)? For primary care and general and family practice physicians, the monopolistically competitive model prevailed over the competing hypotheses--monopoly, perfect competition, and monopolistic competition characterized by consumer informational confusion. Although less conclisive, there is some evidence to support the monopolistically competitive model for surgeons and the consumer informational confusion model for internal medicine physicians.

Strategizing for Intense Competition.

ERIC Educational Resources Information Center

Hahn, William; Bourgeois, Ernest J., Jr.

1999-01-01

Examines trend toward more aggressive student recruiting strategies by colleges and universities, applying a model that assesses five competitive forces-cause and effect of competition, the expanding marketplace, substitute products, buyer power, and supplier power, and examines various strategies for dealing with these competitive forces, such as…

Assessing the Impact of an Autonomous Robotics Competition for STEM Education

ERIC Educational Resources Information Center

Chung, C. J. ChanJin; Cartwright, Christopher; Cole, Matthew

2014-01-01

Robotics competitions for K-12 students are popular, but are students really learning and improving their STEM scores through robotics competitions? If not, why not? If they are, how much more effective is learning through competitions than traditional classes? Is there room for improvement? What is the best robotics competition model to maximize…

Abacavir increases platelet reactivity via competitive inhibition of soluble guanylyl cyclase

PubMed Central

Baum, Paul D.; Sullam, Paul M.; Stoddart, Cheryl A.; McCune, Joseph M.

2011-01-01

Objective To provide a molecular mechanism that explains the association of the antiretroviral guanosine analogue, abacavir, with an increased risk of myocardial infarction. Design Drug effects were studied with biochemical and cellular assays. Methods Human platelets were incubated with nucleoside analogue drugs ex vivo. Platelet activation stimulated by ADP was studied by measuring surface P-selectin with flow cytometry. Inhibition of purified soluble guanylyl cyclase was quantified using an ELISA to measure cGMP production. Results Pre-incubation of platelets in abacavir significantly increased activation in response to ADP in a time and dose-dependent manner. The active anabolite of abacavir, carbovir triphosphate, competitively inhibited soluble guanylyl cyclase activity with a Ki of 55 μmol/l. Conclusion Abacavir competitively inhibits guanylyl cyclase, leading to platelet hyper-reactivity. This may explain the observed increased risk of myocardial infarction in HIV patients taking abacavir. PMID:21941165

Spatial Aspects of Interspecific Competition

NASA Technical Reports Server (NTRS)

Durrett, Rick; Levin, Simon

1998-01-01

Using several variants of a stochastic spatial model introduced by Silvertown et al., we investigate the effect of spatial distribution of individuals on the outcome of competition. First, we prove rigorously that if one species has a competitive advantage over each of the others, then eventually it takes over all the sites in the system. Second, we examine tradeoffs between competition and dispersal distance in a two-species system. Third, we consider a cyclic competitive relationship between three types. In this case, a nonspatial treatment leads to densities that follow neutrally stable cycles or even unstable spiral solutions, while a spatial model yields a stationary distribution with an interesting spatial structure.

Elite Junior Australian Football Players Experience Significantly Different Loads Across Levels of Competition and Training Modes.

PubMed

Lathlean, Timothy J H; Gastin, Paul B; Newstead, Stuart; Finch, Caroline F

2018-07-01

Lathlean, TJH, Gastin, PB, Newstead, S, and Finch, CF. Elite junior Australian football players experience significantly different loads across levels of competition and training modes. J Strength Cond Res 32(7): 2031-2038, 2018-Well-developed physical qualities such as high jumping ability, running endurance, acceleration, and speed can help aspiring junior elite Australian football (AF) players transition to the Australian Football League competition. To do so, players need to experience sufficient load to enhance their physical resilience without increasing their risk of negative outcomes in terms of impaired wellness or injury. The aim of this study was to investigate the differences in load for different levels of competition and training modes across one competitive season. Elite junior AF players (n = 562, aged 17.7 ± 0.3, range: 16-18 years) were recruited from 9 teams across the under-18 state league competition in Victoria. All players recorded their training and match intensities according to the session rating of perceived exertion method. Training sessions were categorized according to skills, strength, conditioning, and other activities, whereas matches were identified according to level of competition. The loads in U18 state league matches (656.7 ± 210.9 au) were significantly higher (p = 0.027) than those in school matches (643.3 ± 260.9 au) and those in U18 representative matches (617.2 ± 175.4). Players, who undertook more than one match per week, experienced significantly less load in subsequent matches (p < 0.001). Furthermore, U18 state league training sessions carried the most load when compared with other training modes. This article highlights that different combinations of training and match involvement affect overall player load, which may predispose players to negative outcomes such as impaired wellness or increased injury risk.

Ontogenetic and evolutionary effects of predation and competition on nine-spined stickleback (Pungitius pungitius) body size.

PubMed

Välimäki, Kaisa; Herczeg, Gábor

2012-07-01

1. Individual- and population-level variation in body size and growth often correlates with many fitness traits. Predation and food availability are expected to affect body size and growth as important agents of both natural selection and phenotypic plasticity. How differences in predation and food availability affect body size/growth during ontogeny in populations adapted to different predation and competition regimes is rarely studied. 2. Nine-spined stickleback (Pungitius pungitius) populations originating from habitats with varying levels of predation and competition are known to be locally adapted to their respective habitats in terms of body size and growth. Here, we studied how different levels of perceived predation risk and competition during ontogeny affect the reaction norms of body size and growth in (i) marine and pond populations adapted to different levels of predation and competition and (ii) different sexes. We reared nine-spined stickleback in a factorial experiment under two levels of perceived predation risk (present/absent) and competition (high/low food supply). 3. We found divergence in the reaction norms at two levels: (i) predation-adapted marine stickleback had stronger reactions to predatory cues than intraspecific competition-adapted pond stickleback, the latter being more sensitive to available food than the marine fish and (ii) females reacting more strongly to the treatments than males. 4. The repeated, habitat-dependent nature of the differences suggests that natural selection is the agent behind the observed patterns. Our results suggest that genetic adaptation to certain environmental factors also involves an increase in the range of expressible phenotypic plasticity. We found support for this phenomenon at two levels: (i) across populations driven by habitat type and (ii) within populations driven by sex. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

The evolution of dispersal in a Levins' type metapopulation model.

PubMed

Jansen, Vincent A A; Vitalis, Renaud

2007-10-01

We study the evolution of the dispersal rate in a metapopulation model with extinction and colonization dynamics, akin to the model as originally described by Levins. To do so we extend the metapopulation model with a description of the within patch dynamics. By means of a separation of time scales we analytically derive a fitness expression from first principles for this model. The fitness function can be written as an inclusive fitness equation (Hamilton's rule). By recasting this equation in a form that emphasizes the effects of competition we show the effect of the local competition and the local population size on the evolution of dispersal. We find that the evolution of dispersal cannot be easily interpreted in terms of avoidance of kin competition, but rather that increased dispersal reduces the competitive ability. Our model also yields a testable prediction in term of relatedness and life-history parameters.

75 FR 63732 - Requirements for Derivatives Clearing Organizations, Designated Contract Markets, and Swap...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-18

... governance of certain DCOs, DCMs, or SEFs or to mitigate systemic risk, promote competition, or mitigate... the clearinghouses to reduce systemic risk, we have the banks now owning the clearinghouses. The... subject to [the CEA] and the avoidance of systemic risk.'' \\20\\ Clearing members contribute substantial...

Competition for space during bacterial colonization of a surface.

PubMed

Lloyd, Diarmuid P; Allen, Rosalind J

2015-09-06

Competition for space is ubiquitous in the ecology of both microorganisms and macro-organisms. We introduce a bacterial model system in which the factors influencing competition for space during colonization of an initially empty habitat can be tracked directly. Using fluorescence microscopy, we follow the fate of individual Escherichia coli bacterial cell lineages as they undergo expansion competition (the race to be the first to colonize a previously empty territory), and as they later compete at boundaries between clonal territories. Our experiments are complemented by computer simulations of a lattice-based model. We find that both expansion competition, manifested as differences in individual cell lag times, and boundary competition, manifested as effects of neighbour cell geometry, can play a role in colonization success, particularly when lineages expand exponentially. This work provides a baseline for investigating how ecological interactions affect colonization of space by bacterial populations, and highlights the potential of bacterial model systems for the testing and development of ecological theory. © 2015 The Authors.

Competition for space during bacterial colonization of a surface

PubMed Central

Lloyd, Diarmuid P.; Allen, Rosalind J.

2015-01-01

Competition for space is ubiquitous in the ecology of both microorganisms and macro-organisms. We introduce a bacterial model system in which the factors influencing competition for space during colonization of an initially empty habitat can be tracked directly. Using fluorescence microscopy, we follow the fate of individual Escherichia coli bacterial cell lineages as they undergo expansion competition (the race to be the first to colonize a previously empty territory), and as they later compete at boundaries between clonal territories. Our experiments are complemented by computer simulations of a lattice-based model. We find that both expansion competition, manifested as differences in individual cell lag times, and boundary competition, manifested as effects of neighbour cell geometry, can play a role in colonization success, particularly when lineages expand exponentially. This work provides a baseline for investigating how ecological interactions affect colonization of space by bacterial populations, and highlights the potential of bacterial model systems for the testing and development of ecological theory. PMID:26333814

Bias Due to Correlation Between Times-at-Risk for Infection in Epidemiologic Studies Measuring Biological Interactions Between Sexually Transmitted Infections: A Case Study Using Human Papillomavirus Type Interactions

PubMed Central

Malagón, Talía; Lemieux-Mellouki, Philippe; Laprise, Jean-François; Brisson, Marc

2016-01-01

The clustering of human papillomavirus (HPV) infections in some individuals is often interpreted as the result of common risk factors rather than biological interactions between different types of HPV. The intraindividual correlation between times-at-risk for all HPV infections is not generally considered in the analysis of epidemiologic studies. We used a deterministic transmission model to simulate cross-sectional and prospective epidemiologic studies measuring associations between 2 HPV types. When we assumed no interactions, the model predicted that studies would estimate odds ratios and incidence rate ratios greater than 1 between HPV types even after complete adjustment for sexual behavior. We demonstrated that this residual association is due to correlation between the times-at-risk for different HPV types, where individuals become concurrently at risk for all of their partners’ HPV types when they enter a partnership and are not at risk when they are single. This correlation can be controlled in prospective studies by restricting analyses to susceptible individuals with an infected sexual partner. The bias in the measured associations was largest in low-sexual-activity populations, cross-sectional studies, and studies which evaluated infection with a first HPV type as the exposure. These results suggest that current epidemiologic evidence does not preclude the existence of competitive biological interactions between HPV types. PMID:27927619

Spatial elements of mortality risk in old-growth forests

USGS Publications Warehouse

Das, Adrian; Battles, John; van Mantgem, Phillip J.; Stephenson, Nathan L.

2008-01-01

For many species of long-lived organisms, such as trees, survival appears to be the most critical vital rate affecting population persistence. However, methods commonly used to quantify tree death, such as relating tree mortality risk solely to diameter growth, almost certainly do not account for important spatial processes. Our goal in this study was to detect and, if present, to quantify the relevance of such processes. For this purpose, we examined purely spatial aspects of mortality for four species, Abies concolor, Abies magnifica, Calocedrus decurrens, and Pinus lambertiana, in an old-growth conifer forest in the Sierra Nevada of California, USA. The analysis was performed using data from nine fully mapped long-term monitoring plots.In three cases, the results unequivocally supported the inclusion of spatial information in models used to predict mortality. For Abies concolor, our results suggested that growth rate may not always adequately capture increased mortality risk due to competition. We also found evidence of a facilitative effect for this species, with mortality risk decreasing with proximity to conspecific neighbors. For Pinus lambertiana, mortality risk increased with density of conspecific neighbors, in keeping with a mechanism of increased pathogen or insect pressure (i.e., a Janzen-Connell type effect). Finally, we found that models estimating risk of being crushed were strongly improved by the inclusion of a simple index of spatial proximity.Not only did spatial indices improve models, those improvements were relevant for mortality prediction. For P. lambertiana, spatial factors were important for estimation of mortality risk regardless of growth rate. For A. concolor, although most of the population fell within spatial conditions in which mortality risk was well described by growth, trees that died occurred outside those conditions in a disproportionate fashion. Furthermore, as stands of A. concolor become increasingly dense, such spatial factors are likely to become increasingly important. In general, models that fail to account for spatial pattern are at risk of failure as conditions change.

Crowd computing: using competitive dynamics to develop and refine highly predictive models.

PubMed

Bentzien, Jörg; Muegge, Ingo; Hamner, Ben; Thompson, David C

2013-05-01

A recent application of a crowd computing platform to develop highly predictive in silico models for use in the drug discovery process is described. The platform, Kaggle™, exploits a competitive dynamic that results in model optimization as the competition unfolds. Here, this dynamic is described in detail and compared with more-conventional modeling strategies. The complete and full structure of the underlying dataset is disclosed and some thoughts as to the broader utility of such 'gamification' approaches to the field of modeling are offered. Copyright © 2013 Elsevier Ltd. All rights reserved.

Reduced risk of sudden death from chest wall blows (commotio cordis) with safety baseballs.

PubMed

Link, Mark S; Maron, Barry J; Wang, Paul J; Pandian, Natesa G; VanderBrink, Brian A; Estes, N A Mark

2002-05-01

In an experimental model of sudden death from baseball chest wall impact (commotio cordis), we sought to determine if sudden death by baseball impact could be reduced with safety baseballs. Sudden cardiac death can occur after chest wall impact with a baseball (commotio cordis). Whether softer-than-standard (safety) baseballs reduce the risk of sudden death is unresolved from the available human data. In a juvenile swine model, ventricular fibrillation (VF) has been shown to be induced reproducibly by precordial impact with a 30-mph baseball 10 to 30 ms before the T-wave peak, and this likelihood was reduced with the softest safety baseballs (T-balls). To further test whether safety baseballs would reduce the risk of sudden death at velocities more relevant to youth sports competition, we used our swine model of commotio cordis to test baseballs propelled at the 40-mph velocity commonly attained in that sport. Forty animals received up to 3 chest wall impacts at 40 mph during the vulnerable period of repolarization for VF with 1 of 3 different safety baseballs of varying hardness, and also by a standard baseball. Safety baseballs propelled at 40 mph significantly reduced the risk for VF. The softest safety baseballs triggered VF in only 11% of impacts, compared with 19% and 22% with safety baseballs of intermediate hardness, and 69% with standard baseballs. In this experimental model of low-energy chest wall impact, safety baseballs reduced (but did not abolish) the risk of sudden cardiac death. More universal use of these safety baseballs may decrease the risk of sudden death on the playing field for young athletes.

Competition for resources can explain patterns of social and individual learning in nature.

PubMed

Smolla, Marco; Gilman, R Tucker; Galla, Tobias; Shultz, Susanne

2015-09-22

In nature, animals often ignore socially available information despite the multiple theoretical benefits of social learning over individual trial-and-error learning. Using information filtered by others is quicker, more efficient and less risky than randomly sampling the environment. To explain the mix of social and individual learning used by animals in nature, most models penalize the quality of socially derived information as either out of date, of poor fidelity or costly to acquire. Competition for limited resources, a fundamental evolutionary force, provides a compelling, yet hitherto overlooked, explanation for the evolution of mixed-learning strategies. We present a novel model of social learning that incorporates competition and demonstrates that (i) social learning is favoured when competition is weak, but (ii) if competition is strong social learning is favoured only when resource quality is highly variable and there is low environmental turnover. The frequency of social learning in our model always evolves until it reduces the mean foraging success of the population. The results of our model are consistent with empirical studies showing that individuals rely less on social information where resources vary little in quality and where there is high within-patch competition. Our model provides a framework for understanding the evolution of social learning, a prerequisite for human cumulative culture. © 2015 The Author(s).

Competition for resources can explain patterns of social and individual learning in nature

PubMed Central

Smolla, Marco; Gilman, R. Tucker; Galla, Tobias; Shultz, Susanne

2015-01-01

In nature, animals often ignore socially available information despite the multiple theoretical benefits of social learning over individual trial-and-error learning. Using information filtered by others is quicker, more efficient and less risky than randomly sampling the environment. To explain the mix of social and individual learning used by animals in nature, most models penalize the quality of socially derived information as either out of date, of poor fidelity or costly to acquire. Competition for limited resources, a fundamental evolutionary force, provides a compelling, yet hitherto overlooked, explanation for the evolution of mixed-learning strategies. We present a novel model of social learning that incorporates competition and demonstrates that (i) social learning is favoured when competition is weak, but (ii) if competition is strong social learning is favoured only when resource quality is highly variable and there is low environmental turnover. The frequency of social learning in our model always evolves until it reduces the mean foraging success of the population. The results of our model are consistent with empirical studies showing that individuals rely less on social information where resources vary little in quality and where there is high within-patch competition. Our model provides a framework for understanding the evolution of social learning, a prerequisite for human cumulative culture. PMID:26354936

Mathematical Modelling of Allelopathy: IV. Assessment of Contributions of Competition and Allelopathy to Interference by Barley

PubMed Central

Liu, De Li; An, Min; Johnson, I.R.; Lovett, J.V.

2005-01-01

One of the main challenges to the research on allelopathy is technically the separation of allelopathic effect from competition, and quantitatively, the assessment of the contribution of each component to overall interference. A simple mathematical model is proposed to calculate the contribution of allelopathy and competition to interference. As an example of applying the quantitative model to interference by barley (Hordeum vulgare cv. Triumph), the approach used was an addition of allelopathic effect, by an equivalent amount, to the environment of the test plant (white mustard, Sinapis alba), rather than elimination of competition. Experiments were conducted in glasshouse to determine the magnitude of the contributions of allelopathy and competition to interference by barley. The leachates of living barley roots significantly reduced the total dry weight of white mustard. The model involved the calculation of adjusted densities to an equivalent basis for modelling the contribution of allelopathy and competition to total interference. The results showed that allelopathy contributed 40%, 37% and 43% to interference by barley at 6, 12 and 18 white mustard pot−1. The consistency in magnitude of the calculated contribution of allelopathic effect by barley across various densities of receiver plant suggested that the adjusted equivalent density is effective and that the model is able to assess the contribution of each component of interference regardless of the density of receiver plant. PMID:19330162

Does competition improve financial stability of the banking sector in ASEAN countries? An empirical analysis.

PubMed

Noman, Abu Hanifa Md; Gee, Chan Sok; Isa, Che Ruhana

2017-01-01

This study examines the influence of competition on the financial stability of the commercial banks of Association of Southeast Asian Nation (ASEAN) over the 1990 to 2014 period. Panzar-Rosse H-statistic, Lerner index and Herfindahl-Hirschman Index (HHI) are used as measures of competition, while Z-score, non-performing loan (NPL) ratio and equity ratio are used as measures of financial stability. Two-step system Generalized Method of Moments (GMM) estimates demonstrate that competition measured by H-statistic is positively related to Z-score and equity ratio, and negatively related to non-performing loan ratio. Conversely, market power measured by Lerner index is negatively related to Z-score and equity ratio and positively related to NPL ratio. These results strongly support the competition-stability view for ASEAN banks. We also capture the non-linear relationship between competition and financial stability by incorporating a quadratic term of competition in our models. The results show that the coefficient of the quadratic term of H-statistic is negative for the Z-score model given a positive coefficient of the linear term in the same model. These results support the non-linear relationship between competition and financial stability of the banking sector. The study contains significant policy implications for improving the financial stability of the commercial banks.

Does competition improve financial stability of the banking sector in ASEAN countries? An empirical analysis

PubMed Central

Gee, Chan Sok; Isa, Che Ruhana

2017-01-01

This study examines the influence of competition on the financial stability of the commercial banks of Association of Southeast Asian Nation (ASEAN) over the 1990 to 2014 period. Panzar-Rosse H-statistic, Lerner index and Herfindahl-Hirschman Index (HHI) are used as measures of competition, while Z-score, non-performing loan (NPL) ratio and equity ratio are used as measures of financial stability. Two-step system Generalized Method of Moments (GMM) estimates demonstrate that competition measured by H-statistic is positively related to Z-score and equity ratio, and negatively related to non-performing loan ratio. Conversely, market power measured by Lerner index is negatively related to Z-score and equity ratio and positively related to NPL ratio. These results strongly support the competition-stability view for ASEAN banks. We also capture the non-linear relationship between competition and financial stability by incorporating a quadratic term of competition in our models. The results show that the coefficient of the quadratic term of H-statistic is negative for the Z-score model given a positive coefficient of the linear term in the same model. These results support the non-linear relationship between competition and financial stability of the banking sector. The study contains significant policy implications for improving the financial stability of the commercial banks. PMID:28486548

Maternal effects, but no good or compatible genes for sperm competitiveness in Australian crickets.

PubMed

Dowling, Damian K; Nystrand, Magdalena; Simmons, Leigh W

2010-05-01

Explanations for the evolution of polyandry often center on the idea that females garner genetic benefits for their offspring by mating multiply. Furthermore, postcopulatory processes are thought to be fundamental to enabling polyandrous females to screen for genetic quality. Much attention has focused on the potential for polyandrous females to accrue such benefits via a sexy- or good-sperm mechanism, whereby additive variation exists among males in sperm competitiveness. Likewise, attention has focused on an alternative model, in which offspring quality (in this context, the sperm competitiveness of sons) hinges on an interaction between parental haplotypes (genetic compatibility). Sperm competitiveness that is contingent on parental compatibility will exhibit nonadditive genetic variation. We tested these models in the Australian cricket, Teleogryllus oceanicus, using a design that allowed us to partition additive, nonadditive genetic, and parental variance for sperm competitiveness. We found an absence of additive and nonadditive genetic variance in this species, challenging the direct relevance of either model to the evolution of sperm competitiveness in particular, and polyandry in general. Instead, we found maternal effects that were possibly sex-linked or cytoplasmically linked. We also found effects of focal male age on sperm competitiveness, with small increments in age conferring more competitive sperm.

Does competition improve health care quality?

PubMed

Scanlon, Dennis P; Swaminathan, Shailender; Lee, Woolton; Chernew, Michael

2008-12-01

To identify the effect of competition on health maintenance organizations' (HMOs) quality measures. Longitudinal analysis of a 5-year panel of the Healthcare Effectiveness Data and Information Set (HEDIS) and Consumer Assessment of Health Plans Survey(R) (CAHPS) data (calendar years 1998-2002). All plans submitting data to the National Committee for Quality Assurance (NCQA) were included regardless of their decision to allow NCQA to disclose their results publicly. NCQA, Interstudy, the Area Resource File, and the Bureau of Labor Statistics. Fixed-effects models were estimated that relate HMO competition to HMO quality controlling for an unmeasured, time-invariant plan, and market traits. Results are compared with estimates from models reliant on cross-sectional variation. Estimates suggest that plan quality does not improve with increased levels of HMO competition (as measured by either the Herfindahl index or the number of HMOs). Similarly, increased HMO penetration is generally not associated with improved quality. Cross-sectional models tend to suggest an inverse relationship between competition and quality. The strategies that promote competition among HMOs in the current market setting may not lead to improved HMO quality. It is possible that price competition dominates, with purchasers and consumers preferring lower premiums at the expense of improved quality, as measured by HEDIS and CAHPS. It is also possible that the fragmentation associated with competition hinders quality improvement.

Market segmentation strategy in internet market

NASA Astrophysics Data System (ADS)

Ren, Yawei; Yang, Deli; Diao, Xinjun

2010-04-01

This paper presents a model to describe the competitive dynamics of web sites on the WWW market and analyze the stability of the model which is composed of one powerful site and two small sites. One of the most important results that emerge from this simple model is that strong competition among websites does not necessarily lead to the demise of the small website on the WWW market. From the stability analysis of the model, we obtain a series of conditions in which small sites can obtain competitive advantages by using the market segmentation strategy.

Competitions hatch butterfly attractors in foreign exchange markets

NASA Astrophysics Data System (ADS)

Jin, Yu Ying

2005-03-01

Chaos in foreign exchange markets is a common issue of concern in the study of economic dynamics. In this work, we mainly investigate the competition effect on chaos in foreign exchange markets. As one of the main economic structures in the globalization process, competition between two target exchange rates with the same base currency forms a simple competitive exchange rate relation, where each exchange rate follows the chaotic model of De Grauwe (Exchange Rate Theory-Chaotic Models of Foreign Exchange Markets, Blackwell, Oxford, Cambridge, MA, 1993). The main discovery is, while each exchange rate is in its non-chaotic parameter regions, the effect of competition will “hatch” butterfly-like chaotic attractors in the competitive market. The positive Lyapunov exponent in the market explains the reason why chaos occurs.

Multi-species coexistence in Lotka-Volterra competitive systems with crowding effects.

PubMed

Gavina, Maica Krizna A; Tahara, Takeru; Tainaka, Kei-Ichi; Ito, Hiromu; Morita, Satoru; Ichinose, Genki; Okabe, Takuya; Togashi, Tatsuya; Nagatani, Takashi; Yoshimura, Jin

2018-01-19

Classical Lotka-Volterra (LV) competition equation has shown that coexistence of competitive species is only possible when intraspecific competition is stronger than interspecific competition, i.e., the species inhibit their own growth more than the growth of the other species. Note that density effect is assumed to be linear in a classical LV equation. In contrast, in wild populations we can observed that mortality rate often increases when population density is very high, known as crowding effects. Under this perspective, the aggregation models of competitive species have been developed, adding the additional reduction in growth rates at high population densities. This study shows that the coexistence of a few species is promoted. However, an unsolved question is the coexistence of many competitive species often observed in natural communities. Here, we build an LV competition equation with a nonlinear crowding effect. Our results show that under a weak crowding effect, stable coexistence of many species becomes plausible, unlike the previous aggregation model. An analysis indicates that increased mortality rate under high density works as elevated intraspecific competition leading to the coexistence. This may be another mechanism for the coexistence of many competitive species leading high species diversity in nature.

Intraspecific competition reduces niche width in experimental populations

PubMed Central

Parent, Christine E; Agashe, Deepa; Bolnick, Daniel I

2014-01-01

Intraspecific competition is believed to drive niche expansion, because otherwise suboptimal resources can provide a refuge from competition for preferred resources. Competitive niche expansion is well supported by empirical observations, experiments, and theory, and is often invoked to explain phenotypic diversification within populations, some forms of speciation, and adaptive radiation. However, some foraging models predict the opposite outcome, and it therefore remains unclear whether competition will promote or inhibit niche expansion. We conducted experiments to test whether competition changes the fitness landscape to favor niche expansion, and if competition indeed drives niche expansion as expected. Using Tribolium castaneum flour beetles fed either wheat (their ancestral resource), corn (a novel resource) or mixtures of both resources, we show that fitness is maximized on a mixed diet. Next, we show that at higher population density, the optimal diet shifts toward greater use of corn, favoring niche expansion. In stark contrast, when beetles were given a choice of resources, we found that competition caused niche contraction onto the ancestral resource. This presents a puzzling mismatch between how competition alters the fitness landscape, versus competition's effects on resource use. We discuss several explanations for this mismatch, highlighting potential reasons why optimality models might be misleading. PMID:25505525

Modeling of the competition life cycle using the software complex of cellular automata PyCAlab

NASA Astrophysics Data System (ADS)

Berg, D. B.; Beklemishev, K. A.; Medvedev, A. N.; Medvedeva, M. A.

2015-11-01

The aim of the work is to develop a numerical model of the life cycle of competition on the basis of software complex cellular automata PyCAlab. The model is based on the general patterns of growth of various systems in resource-limited settings. At examples it is shown that the period of transition from an unlimited growth of the market agents to the stage of competitive growth takes quite a long time and may be characterized as monotonic. During this period two main strategies of competitive selection coexist: 1) capture of maximum market space with any reasonable costs; 2) saving by reducing costs. The obtained results allow concluding that the competitive strategies of companies must combine two mentioned types of behavior, and this issue needs to be given adequate attention in the academic literature on management. The created numerical model may be used for market research when developing of the strategies for promotion of new goods and services.

Predicting coexistence of plants subject to a tolerance-competition trade-off.

PubMed

Haegeman, Bart; Sari, Tewfik; Etienne, Rampal S

2014-06-01

Ecological trade-offs between species are often invoked to explain species coexistence in ecological communities. However, few mathematical models have been proposed for which coexistence conditions can be characterized explicitly in terms of a trade-off. Here we present a model of a plant community which allows such a characterization. In the model plant species compete for sites where each site has a fixed stress condition. Species differ both in stress tolerance and competitive ability. Stress tolerance is quantified as the fraction of sites with stress conditions low enough to allow establishment. Competitive ability is quantified as the propensity to win the competition for empty sites. We derive the deterministic, discrete-time dynamical system for the species abundances. We prove the conditions under which plant species can coexist in a stable equilibrium. We show that the coexistence conditions can be characterized graphically, clearly illustrating the trade-off between stress tolerance and competitive ability. We compare our model with a recently proposed, continuous-time dynamical system for a tolerance-fecundity trade-off in plant communities, and we show that this model is a special case of the continuous-time version of our model.

Contagious diseases in competitive sport: what are the risks?

PubMed

Dorman, J M

2000-11-01

Great concern is often expressed over the possibility of contagion among athletes in competitive sports, particularly sports with much person-to-person contact. Human immunodeficiency virus (HIV) is only the most notorious of infectious agents; potentially, other viruses, bacteria, and even fungi may be involved. Because of the concern, however, special attention is paid to HIV and hepatitis B infections. For most of the infections considered, the athlete is more at risk during activities off the playing field than while competing. Inclusion of immunizations against measles and hepatitis B among prematriculation immunization requirements (PIRs) for colleges and universities would eliminate these two diseases from the list of dangers to college athletes and all students. Education, rather than regulations, should remain the cornerstone in considering the risks to athletes from contagious diseases.

Sport Participation and the Risk of Anterior Cruciate Ligament Reconstruction in Adolescents: A Population-based Prospective Cohort Study (The Young-HUNT Study).

PubMed

Johnsen, Marianne Bakke; Guddal, Maren Hjelle; Småstuen, Milada Cvancarova; Moksnes, Håvard; Engebretsen, Lars; Storheim, Kjersti; Zwart, John-Anker

2016-11-01

An anterior cruciate ligament (ACL) injury is a severe injury that may require ACL reconstruction (ACLR) to enable the return to sport. Risk factors for ACLR have not firmly been established in the general adolescent population. To investigate the incidence and risk factors for ACLR in a population-based cohort of adolescents. Cohort study; Level of evidence, 3. We prospectively followed 7644 adolescents from the adolescent part of the Nord-Trøndelag Health Study, included from 2006 to 2008. The main risk factors of interest were the level of sport participation (level I, II, or III) and sport competitions. The endpoint was primary ACLR recorded in the Norwegian National Knee Ligament Registry between January 2006 and December 2013. A total of 3808 boys and 3836 girls were included in the analyses. We identified 69 (0.9%) ACLRs with a median of 7.3 years of follow-up, providing an overall ACLR incidence of 38.9 (95% CI, 30.7-49.3) per 100,000 person-years. The hazard ratio (HR) for ACLR associated with level I sport participation was 3.93 (95% CI, 0.92-16.80) for boys and 3.31 (95% CI, 1.30-8.43) for girls. There was a stronger association related to participating in sport competitions. Girls had over 5 times a higher risk (HR, 5.42; 95% CI, 2.51-11.70) and boys over 4 times the risk (HR, 4.22; 95% CI, 1.58-11.30) of ACLR compared with those who did not compete. Participating in level I sports and sport competitions significantly increased the risk of undergoing primary ACLR. Preventive strategies should be implemented to reduce the incidence and future burden of ACLR. © 2016 The Author(s).

Training-related and competition-related risk factors for respiratory tract and gastrointestinal infections in elite cross-country skiers.

PubMed

Svendsen, Ida S; Taylor, Ian M; Tønnessen, Espen; Bahr, Roald; Gleeson, Michael

2016-07-01

To examine symptoms indicative of respiratory tract and gastrointestinal infections and determine risk factors for such symptoms in elite cross-country skiers. Self-reported training and symptom data for 37 elite cross-country skiers from 2007 to 2015 were analysed using multilevel logistic regression equations with symptom incidence and duration as outcome variables, and sex, performance level, season, competition, air travel, altitude exposure and training characteristics as independent variables. Data for 7016 person-weeks were analysed, including 464 self-reported infection events and 110 959 h of training. Athletes reported median (range) 3 (1-7) respiratory tract and/or gastrointestinal events per year, with symptoms lasting 5 (1-24) days. During the winter, symptoms occurred more frequently (OR 2.09, p<0.001) and lasted longer (b=0.043, p<0.001) compared with summer. Competition and air travel increased the risk of symptoms, with ORs of 2.93 (95% CI 2.24 to 3.83) and 4.94 (95% CI 3.74 to 6.53), respectively (p<0.001). Athletes with higher training monotony had lower risk of symptoms (OR 0.87 (95% CI 0.73 to 0.99), p<0.05). Other training variables were not associated with symptoms. Athletes who had won an Olympic/World Championship medal reported shorter symptom duration compared with less successful athletes (b=-0.019, p<0.05) resulting in significantly fewer symptomatic days/year (14 (6-29) vs 22 (8-43) days/year). Air travel and competition are major risk factors for acute respiratory tract and gastrointestinal symptoms in this population. Athletes who have large fluctuations in training load experience such symptoms more frequently. Shorter duration of symptoms appears to be associated with success in cross-country skiing. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Ontology-Based Model Of Firm Competitiveness

NASA Astrophysics Data System (ADS)

Deliyska, Boryana; Stoenchev, Nikolay

2010-10-01

Competitiveness is important characteristics of each business organization (firm, company, corporation etc). It is of great significance for the organization existence and defines evaluation criteria of business success at microeconomical level. Each criterium comprises set of indicators with specific weight coefficients. In the work an ontology-based model of firm competitiveness is presented as a set of several mutually connected ontologies. It would be useful for knowledge structuring, standardization and sharing among experts and software engineers who develop application in the domain. Then the assessment of the competitiveness of various business organizations could be generated more effectively.

A model for competitiveness level analysis in sports competitions: Application to basketball

NASA Astrophysics Data System (ADS)

de Saá Guerra, Y.; Martín González, J. M.; Sarmiento Montesdeoca, S.; Rodríguez Ruiz, D.; García-Rodríguez, A.; García-Manso, J. M.

2012-05-01

The degree of overall competitiveness of a sport league is a complex phenomenon. It is difficult to assess and quantify all elements that yield the final standing. In this paper, we analyze the general behavior of the result matrices of each season and we use the corresponding results as a probably density. Thus, the results of previous seasons are a way to investigate the probability that each team has to reach a certain number of victories. We developed a model based on Shannon entropy using two extreme competitive structures (a hierarchical structure and a random structure), and applied this model to investigate the competitiveness of two of the best professional basketball leagues: the NBA (USA) and the ACB (Spain). Both leagues’ entropy levels are high (NBA mean 0.983; ACB mean 0.980), indicating high competitiveness, although the entropy of the ACB (from 0.986 to 0.972) demonstrated more seasonal variability than that of the NBA (from 0.985 to 0.990), a possible result of greater sporting gradients in the ACB. The use of this methodology has proven useful for investigating the competitiveness of sports leagues as well as their underlying variability across time.

Oral Interpretation and Broadcasting at Individual Events Tournaments: An Interdisciplinary Tournament Model.

ERIC Educational Resources Information Center

Drake, Harold L.

Since the American Forensic Association has sanctioned recording individual events competition, it might be in the interest of competition to combine oral interpretation and radio/television broadcast competition into simultaneous competition. Voice development is a goal shared by oral interpretation and broadcasting, so oral interpretation…

Intraspecific maternal competition induces summer diapause in insect parasitoids.

PubMed

Tougeron, Kévin; Hraoui, George; Le Lann, Cécile; van Baaren, Joan; Brodeur, Jacques

2017-06-15

Organisms often live in unpredictable environments and have to adopt life history strategies that optimize their fitness under these conditions. According to bet-hedging theory, individuals can reduce variation in fitness outcomes by investing in different strategies at the same time. For arthropods, facultative summer diapause enables survival during dry and hot periods of the year, and can be triggered by a decrease in resource abundance. However, the effect of resource depletion on diapause induction has never been disentangled from the effect of the perception of the presence of competitors. Using two solitary parasitoid species of cereal aphids as a model system, Aphidius avenae (Haliday) and Aphidius rhopalosiphi (De Stefani-Perez) (Hymenoptera: Braconidae), we tested whether (i) low absolute host density and/or (ii) high levels of parasitoid females' competition lead to maternal-induced summer diapause in parasitoid offspring. Under summer-like climatic conditions, emerging parasitoid females were (i) reared alone and exposed to different host densities (from 5 to 130 aphids), or (ii) reared together with competing females (from 2 to 20 females) and then exposed individually to 50 aphids. For both parasitoid species, low aphid densities did not induce summer diapause. However, the incidence of summer diapause increased up to a maximum of 11% with increasing levels of competition experienced by female parasitoids. More than 60% of the females produced both diapausing and nondiapausing offspring after being kept at the two highest competition densities. Such a "spreading-the-risk" strategy has likely evolved to optimize parasitoid fitness by preventing the following generation from exposure to low populations of suitable hosts and high mortality from superparasitism. These results provide the first experimental evidence of direct maternal competition-induced diapause in insects, and may change the way we apprehend the evolution of arthropod seasonal ecology, by considering intraspecific competition. © 2017 Institute of Zoology, Chinese Academy of Sciences.

Numerical modeling of transverse mode competition in strongly pumped multimode fiber lasers and amplifiers.

PubMed

Gong, Mali; Yuan, Yanyang; Li, Chen; Yan, Ping; Zhang, Haitao; Liao, Suying

2007-03-19

A model based on propagation-rate equations with consideration of transverse gain distribution is built up to describe the transverse mode competition in strongly pumped multimode fiber lasers and amplifiers. An approximate practical numerical algorithm by multilayer method is presented. Based on the model and the numerical algorithm, the behaviors of multitransverse mode competition are demonstrated and individual transverse modes power distributions of output are simulated numerically for both fiber lasers and amplifiers under various conditions.

Sports injuries surveillance during the 2007 IAAF World Athletics Championships.

PubMed

Alonso, Juan Manuel; Junge, Astrid; Renström, Per; Engebretsen, Lars; Mountjoy, Margo; Dvorak, Jiri

2009-01-01

The aim of this study was to analyze all sports injuries incurred in competitions and/or training during the 2007 World Athletics Championships and to prove the feasibility of the injury surveillance system developed for the 2008 Olympic Games for individual sports. Prospective recording of injuries. 11 IAAF World Championships in Athletics 2007 in Osaka, Japan. All national team physicians and physiotherapists; Local Organising Committee (LOC) physicians working in the Medical Centres at the stadium and warm-up area. Frequency, characteristics, and incidence of injuries. 192 injuries were reported, resulting in an incidence of 97 injuries per 1000 registered athletes. More than half of the injuries (56%) were expected to prevent the athlete from participating in competition or training. Eighty percent affected the lower extremity; the most common diagnosis was thigh strain (16%). In most cases, the injury was caused by overuse (44%). A quarter of the injuries were incurred during training and 137 (71%) in competition. On average, 72.4 injuries per 1000 competing athletes were incurred in competitions. The incidence of injury varied substantially among the disciplines. The risk of a time-loss injury was highest in heptathlon, women's 10,000 m, women's 3000 m steeplechase, decathlon, and men's marathon. The injury surveillance system proved feasible for individual sports. Risk of injury varied among the disciplines, with highest risk in combined disciplines, steeplechase, and long-distance runs. Preventive interventions should mainly focus on overuse injuries and adequate rehabilitation of previous injuries.

A Novel TRM Calculation Method by Probabilistic Concept

NASA Astrophysics Data System (ADS)

Audomvongseree, Kulyos; Yokoyama, Akihiko; Verma, Suresh Chand; Nakachi, Yoshiki

In a new competitive environment, it becomes possible for the third party to access a transmission facility. From this structure, to efficiently manage the utilization of the transmission network, a new definition about Available Transfer Capability (ATC) has been proposed. According to the North American ElectricReliability Council (NERC)’s definition, ATC depends on several parameters, i. e. Total Transfer Capability (TTC), Transmission Reliability Margin (TRM), and Capacity Benefit Margin (CBM). This paper is focused on the calculation of TRM which is one of the security margin reserved for any uncertainty of system conditions. The TRM calculation by probabilistic method is proposed in this paper. Based on the modeling of load forecast error and error in transmission line limitation, various cases of transmission transfer capability and its related probabilistic nature can be calculated. By consideration of the proposed concept of risk analysis, the appropriate required amount of TRM can be obtained. The objective of this research is to provide realistic information on the actual ability of the network which may be an alternative choice for system operators to make an appropriate decision in the competitive market. The advantages of the proposed method are illustrated by application to the IEEJ-WEST10 model system.

Grazer-induced morphological defense in Scenedesmus obliquus is affected by competition against Microcystis aeruginosa

PubMed Central

Zhu, Xuexia; Wang, Jun; Lu, Yichun; Chen, Qinwen; Yang, Zhou

2015-01-01

The green alga Scenedesmus is known for its phenotypic plasticity in response to grazing risk. However, the benefits of colony formation induced by infochemicals from zooplankton should come with costs. That is, a tradeoff in benefit-to-cost ratios is likely under complex environmental conditions. In this study, we hypothesized that the coexistence of Scenedesmus and its competitors decreases the formation of anti-grazer colonies in Scenedesmus. Results demonstrated that the presence of a competitor Microcystis aeruginosa inhibited inducible defensive colony formation of Scenedesmus obliquus, and the established defensive colonies negatively affected the competitive ability of S. obliquus. The proportion of induced defensive colonies in cultures was dependent on the relative abundance of competitors. Under low competition intensity, large amount of eight-celled colonies were formed but at the cost of decreased competitive inhibition on M. aeruginosa. By contrast, defensive colony formation of S. obliquus slacked in the presence of high competition intensity to maintain a high displacement rate (competitive ability). In conclusion, S. obliquus exhibited different responses to potential grazing pressure under different intensities of competition, i.e., Scenedesmus morphological response to grazing infochemicals was affected by competition against Microcystis. PMID:26224387

Grazer-induced morphological defense in Scenedesmus obliquus is affected by competition against Microcystis aeruginosa.

PubMed

Zhu, Xuexia; Wang, Jun; Lu, Yichun; Chen, Qinwen; Yang, Zhou

2015-07-30

The green alga Scenedesmus is known for its phenotypic plasticity in response to grazing risk. However, the benefits of colony formation induced by infochemicals from zooplankton should come with costs. That is, a tradeoff in benefit-to-cost ratios is likely under complex environmental conditions. In this study, we hypothesized that the coexistence of Scenedesmus and its competitors decreases the formation of anti-grazer colonies in Scenedesmus. Results demonstrated that the presence of a competitor Microcystis aeruginosa inhibited inducible defensive colony formation of Scenedesmus obliquus, and the established defensive colonies negatively affected the competitive ability of S. obliquus. The proportion of induced defensive colonies in cultures was dependent on the relative abundance of competitors. Under low competition intensity, large amount of eight-celled colonies were formed but at the cost of decreased competitive inhibition on M. aeruginosa. By contrast, defensive colony formation of S. obliquus slacked in the presence of high competition intensity to maintain a high displacement rate (competitive ability). In conclusion, S. obliquus exhibited different responses to potential grazing pressure under different intensities of competition, i.e., Scenedesmus morphological response to grazing infochemicals was affected by competition against Microcystis.

78 FR 32865 - Procedures To Establish Appropriate Minimum Block Sizes for Large Notional Off-Facility Swaps and...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-31

... Financial Integrity of Markets c. Price Discovery d. Sound Risk Management Practices e. Other Public... Discovery d. Sound Risk Management Practices e. Other Public Interest Considerations E. Costs and Benefits..., Competitiveness and Financial Integrity c. Price Discovery d. Sound Risk Management Practices e. Other Public...

The Strategic and Legal Risks of Work-Integrated Learning: An Enterprise Risk Management Perspective

ERIC Educational Resources Information Center

Cameron, Craig

2017-01-01

Work-integrated learning (WIL) is a risky business for universities. WIL is a strategic risk worthy of pursuing by universities in the prevailing higher education environment, which is characterized by competition, changes in funding arrangements and stakeholder demand for WIL. Nevertheless the strategic opportunities that WIL presents cannot be…

Competitive bidding for health insurance contracts.

PubMed

Keijser, G M; Kirkman-Liff, B L

1992-05-01

The determination of the payment or premium to be paid to the insurer by a large purchaser of care must accurately represent the risk of the enrolled persons. One approach is a risk-adjusted payment established by a mathematical formula, which estimates the effect of many variables on total care costs, and for different groups of persons determine an average cost. This method has several problems, and an alternative is competitive bidding. Market forces pressure providers to offer the lowest possible bids while attempting to remain fiscally viable and provide high-quality services. Research from the U.S. demonstrates that competitive contracting effectively lowered the costs of health care for those sectors of the health care system that used this strategy. Bidding by area gave far more equitable results than could have been obtained with a state-wide system with crude adjustments for each area. It is an alternative which can create strong incentives for innovation and cost-containment, and at the same time allows insurers to take into account local variation in supply and demand of care. As a potential alternative to a regulatory system, competitive bidding should be considered for regional experimentation in health insurer payment.

Extreme event medicine: considerations for the organisation of out-of-hospital care during obstacle, adventure and endurance competitions.

PubMed

Laskowski-Jones, Linda; Caudell, Michael J; Hawkins, Seth C; Jones, Lawrence J; Dymond, Chelsea A; Cushing, Tracy; Gupta, Sanjey; Young, David S; Starling, Jennifer M; Bounds, Richard

2017-10-01

Obstacle, adventure and endurance competitions in challenging or remote settings are increasing in popularity. A literature search indicates a dearth of evidence-based research on the organisation of medical care for wilderness competitions. The organisation of medical care for each event is best tailored to specific race components, participant characteristics, geography, risk assessments, legal requirements, and the availability of both local and outside resources. Considering the health risks and logistical complexities inherent in these events, there is a compelling need for guiding principles that bridge the fields of wilderness medicine and sports medicine in providing a framework for the organisation of medical care delivery during wilderness and remote obstacle, adventure and endurance competitions. This narrative review, authored by experts in wilderness and operational medicine, provides such a framework. The primary goal is to assist organisers and medical providers in planning for sporting events in which participants are in situations or locations that exceed the capacity of local emergency medical services resources. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Contribution of European research to risk analysis.

PubMed

Boenke, A

2001-12-01

The European Commission's, Quality of Life Research Programme, Key Action 1-Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety, of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches, harmonization of risk assessment principles methodologies and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries, to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women, evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.

Entry and Exit.

DTIC Science & Technology

1987-03-01

1. Introduction R Analyses of industrial competition have attained a new vigor with the application of game -theoretic methods. The process of... competition is represented in models that reflect genuine struggles for entry, market power, and continuing survival. Dynamics and informational effects are...presents a few of the models developed recently to study competitive processes that affect a firm’s entry into a market , and the decision to exit. The

Computer Science Career Network

DTIC Science & Technology

2013-03-01

development model. TopCoder’s development model is competition-based, meaning that TopCoder conducts competitions to develop digital assets. TopCoder...success in running a competition that had as an objective creating digital assets, and we intend to run more of them, to create assets for...cash prizes and merchandise . This includes social media contests, contests will all our games, special referral contests, and a couple NASA

Using simulation models to investigate the cumulative effects of sowing rate, sowing date and cultivar choice on weed competition.

PubMed

Andrew, Izzadora K S; Storkey, Jonathan

2017-05-01

With the increasing pressure on crop production from the evolution of herbicide resistance, farmers are increasingly adopting Integrated Weed Management (IWM) strategies to augment their weed control. These include measures to increase the competitiveness of the crop canopy such as increased sowing rate and the use of more competitive cultivars. While there are data on the relative impact of these non-chemical weed control methods assessed in isolation, there is uncertainty about their combined contribution, which may be hindering their adoption. In this article, the INTERCOM simulation model of crop/weed competition was used to examine the combined impact of crop density, sowing date and cultivar choice on the outcomes of competition between wheat ( Triticum aestivum ) and Alopecurus myosuroides . Alopecurus myosuroides is a problematic weed of cereal crops in North-Western Europe and the primary target for IWM in the UK because it has evolved resistance to a range of herbicides. The model was parameterised for two cultivars with contrasting competitive ability, and simulations run across 10 years at different crop densities and two sowing dates. The results suggest that sowing date, sowing density and cultivar choice largely work in a complementary fashion, allowing enhanced competitive ability against weeds when used in combination. However, the relative benefit of choosing a more competitive cultivar decreases at later sowing dates and higher crop densities. Modeling approaches could be further employed to examine the effectiveness of IWM, reducing the need for more expensive and cumbersome long-term in situ experimentation.

Risk management in the competitive electric power industry

NASA Astrophysics Data System (ADS)

Dahlgren, Robert William

From 1990 until present day, the electric power industry has experienced dramatic changes worldwide. This recent evolution of the power industry has included creation and multiple iterations of competitive wholesale markets in many different forms. The creation of these competitive markets has resulted in increased short-term volatility of power prices. Vertically integrated utilities emerged from years of regulatory controls to now experience the need to perform risk assessment. The goal of this dissertation is to provide background and details of the evolution of market structures combined with examples of how to apply price risk assessment techniques such as Value-at-Risk (VaR). In Chapter 1, the history and evolution of three selected regional markets, PJM, California, and England and Wales is presented. A summary of the commonalities and differences is presented to provide an overview of the rate of transformation of the industry in recent years. The broad area of risk management in the power industry is also explored through a State-of-the-Art Literature Survey. In Chapter 2, an illustration of risk assessment to power trading is presented. The techniques of Value-at-Risk and Conditional Value-at-Risk are introduced and applied to a common scenario. The advantages and limitations of the techniques are compared through observation of their results against the common example. Volatility in the California Power Markets is presented in Chapter 3. This analysis explores the California markets in the summer of 2000 including the application of VaR analysis to the extreme volatility observed during this period. In Chapter 4, CVaR is applied to the same California historical data used in Chapter 3. In addition, the unique application of minimizing the risk of a power portfolio by minimizing CVaR is presented. The application relies on recent research into CVaR whereby the portfolio optimization problem can be reduced to a Linear Programming problem.

Defining strategies to win in the Internet market

NASA Astrophysics Data System (ADS)

López, Luis; Sanjuán, Miguel A. F.

2001-12-01

This paper analyzes a model for the competition dynamics of web sites in the Internet, based on the Lotka-Volterra competition equations. This model shows the well known appearance of a winner-take-all characteristic and is based in the nonvalidity of traditional offer and demand equilibrium theory of these kinds of markets. From the stability analysis of the model, we establish a series of rules which are useful for defining strategies in the Internet market. One of the most important results that emerge from this simple model is the appearance of some unexpected phenomena related to the collaboration and competition between sites.

Teaching Imperfect Competition at the Principles Level.

ERIC Educational Resources Information Center

Weber, William V.; Highfill, Jannett K.

1990-01-01

Argues that, although most economics textbooks' explanations of imperfect competition may involve three to five models, the concept can be taught using a single, simple model. Uses several business/economic examples as illustrations. (DB)

The Role of Culture, Competitiveness and Economic Performance in Explaining Academic Performance: A Global Market Analysis for International Student Segmentation

ERIC Educational Resources Information Center

Baumann, Chris; Hamin

2011-01-01

A nation's culture, competitiveness and economic performance explain academic performance. Partial Least Squares (PLS) testing of 2252 students shows culture affects competitiveness and academic performance. Culture and economic performance each explain 32%; competitiveness 36%. The model predicts academic performance when culture, competitiveness…

The Effect of Coaches’ Controlling Style on the Competitive Anxiety of Young Athletes

PubMed Central

Ramis, Yago; Torregrosa, Miquel; Viladrich, Carme; Cruz, Jaume

2017-01-01

Framed on a Self-Determination Theory perspective, the purpose of this study was to explore the predictive capacity of coaches’ interpersonal controlling style on the competitive anxiety of young athletes, considering the mediating effect of the athletes’ controlled motivation on this relationship. The sample consisted of 1166 athletes, aged between 9 and 18, who ranked their perceptions of coaches’ controlling style, as well as the reasons for participating in sport and their competitive anxiety before or during competition. The structural models assessing both the direct effect of the controlling style on the anxiety and the complete mediated effect of the controlled motivation on this relationship revealed good fit indices. However, a significant difference of the chi-square was obtained when comparing these models to the partial mediation model, providing evidence of this last model to be more adequate to describe the relationship between coaches’ controlling style and athletes’ competitive anxiety. Positive significant effects of coach controlling style on the three forms of competitive anxiety were found (βCS-SA = 0.21, p < 0.001; βCS-W= 0.14, p < 0.001; βCS-CD= 0.30, p < 0.001) indicating that coach controlling style could be an antecedent for athletes’ anxiety in a direct way. Although this style also predicts athletes’ motivation to participate, this indirect path seems to predict competitive anxiety in a less clear way. We discuss our results facing them up to Vallerand’s hierarchical model postulates, focusing on the relevant influence of coaches on the young athletes’ experience in the sport context. PMID:28446892

Male-biased sex ratio does not promote increased sperm competitiveness in the seed beetle, Callosobruchus maculatus.

PubMed

McNamara, Kathryn B; Robinson, Stephen P; Rosa, Márta E; Sloan, Nadia S; van Lieshout, Emile; Simmons, Leigh W

2016-06-16

Sperm competition risk and intensity can select for adaptations that increase male fertilisation success. Evolutionary responses are examined typically by generating increased strength of sexual selection via direct manipulation of female mating rates (by enforcing monandry or polyandry) or by alteration of adult sex ratios. Despite being a model species for sexual selection research, the effect of sexual selection intensity via adult sex-ratio manipulation on male investment strategies has not been investigated in the seed beetle, Callosobruchus maculatus. We imposed 32 generations of experimental evolution on 10 populations of beetles by manipulating adult sex ratio. Contrary to predictions, males evolving in male-biased populations did not increase their testes and accessory gland size. This absence of divergence in ejaculate investment was also reflected in the fact that males from male-biased populations were not more successful in either preventing females from remating, or in competing directly for fertilisations. These populations already demonstrate divergence in mating behaviour and immunity, suggesting sufficient generations have passed to allow divergence in physiological and behavioural traits. We propose several explanations for the absence of divergence in sperm competitiveness among our populations and the pitfalls of using sex ratio manipulation to assess evolutionary responses to sexual selection intensity.

Male-biased sex ratio does not promote increased sperm competitiveness in the seed beetle, Callosobruchus maculatus

PubMed Central

McNamara, Kathryn B.; Robinson, Stephen P.; Rosa, Márta E.; Sloan, Nadia S.; van Lieshout, Emile; Simmons, Leigh W.

2016-01-01

Sperm competition risk and intensity can select for adaptations that increase male fertilisation success. Evolutionary responses are examined typically by generating increased strength of sexual selection via direct manipulation of female mating rates (by enforcing monandry or polyandry) or by alteration of adult sex ratios. Despite being a model species for sexual selection research, the effect of sexual selection intensity via adult sex-ratio manipulation on male investment strategies has not been investigated in the seed beetle, Callosobruchus maculatus. We imposed 32 generations of experimental evolution on 10 populations of beetles by manipulating adult sex ratio. Contrary to predictions, males evolving in male-biased populations did not increase their testes and accessory gland size. This absence of divergence in ejaculate investment was also reflected in the fact that males from male-biased populations were not more successful in either preventing females from remating, or in competing directly for fertilisations. These populations already demonstrate divergence in mating behaviour and immunity, suggesting sufficient generations have passed to allow divergence in physiological and behavioural traits. We propose several explanations for the absence of divergence in sperm competitiveness among our populations and the pitfalls of using sex ratio manipulation to assess evolutionary responses to sexual selection intensity. PMID:27306351

Competition for hummingbird pollination shapes flower color variation in Andean solanaceae.

PubMed

Muchhala, Nathan; Johnsen, Sönke; Smith, Stacey Dewitt

2014-08-01

One classic explanation for the remarkable diversity of flower colors across angiosperms involves evolutionary shifts among different types of pollinators with different color preferences. However, the pollinator shift model fails to account for the many examples of color variation within clades that share the same pollination system. An alternate explanation is the competition model, which suggests that color divergence evolves in response to interspecific competition for pollinators, as a means to decrease interspecific pollinator movements. This model predicts color overdispersion within communities relative to null assemblages. Here, we combine morphometric analyses, field surveys, and models of pollinator vision with a species-level phylogeny to test the competition model in the primarily hummingbird-pollinated clade Iochrominae (Solanaceae). Results show that flower color as perceived by pollinators is significantly overdispersed within sites. This pattern is not simply due to phylogenetic history: phylogenetic community structure does not deviate from random expectations, and flower color lacks phylogenetic signal. Moreover, taxa that occur in sympatry occupy a significantly larger volume of color space than those in allopatry, supporting the hypothesis that competition in sympatry drove the evolution of novel colors. We suggest that competition among close relatives may commonly underlie floral divergence, especially in species-rich habitats where congeners frequently co-occur. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Sustainable Competitive Advantage for Educational Institutions: A Suggested Model.

ERIC Educational Resources Information Center

Mazzarol, Tim; Soutar, Geoffrey Norman

1999-01-01

Outlines a model of factors critical to establishing and maintaining sustainable competitive advantage for education-services enterprises in international markets. The model, which combines industrial economics, management theory, and services marketing, seeks to explain the strategic decision-making environment in which the education exporter…

The Real Transformation: Building and Maintaining Long-Term Competitive Advantage

DTIC Science & Technology

2003-01-01

TERM COMPETITIVE ADVANTAGE LTC EDWARD C. CARDON, USA A TRANFORMATION PAPER FOR THE CHAIRMAN OF THE JOINT CHIEFS OF STAFF SEMINAR...SUBTITLE The Real Transformation: Building and Maintaining Long-Term Competitive Advantage 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...long-term military competitive advantage in comparison to the rest of the world.4 This approach suggests a model that places competition as the

The Epidemiology of Injuries Across the Weight-Training Sports.

PubMed

Keogh, Justin W L; Winwood, Paul W

2017-03-01

Weight-training sports, including weightlifting, powerlifting, bodybuilding, strongman, Highland Games, and CrossFit, are weight-training sports that have separate divisions for males and females of a variety of ages, competitive standards, and bodyweight classes. These sports may be considered dangerous because of the heavy loads commonly used in training and competition. Our objective was to systematically review the injury epidemiology of these weight-training sports, and, where possible, gain some insight into whether this may be affected by age, sex, competitive standard, and bodyweight class. We performed an electronic search using PubMed, SPORTDiscus, CINAHL, and Embase for injury epidemiology studies involving competitive athletes in these weight-training sports. Eligible studies included peer-reviewed journal articles only, with no limit placed on date or language of publication. We assessed the risk of bias in all studies using an adaption of the musculoskeletal injury review method. Only five of the 20 eligible studies had a risk of bias score ≥75 %, meaning the risk of bias in these five studies was considered low. While 14 of the studies had sample sizes >100 participants, only four studies utilized a prospective design. Bodybuilding had the lowest injury rates (0.12-0.7 injuries per lifter per year; 0.24-1 injury per 1000 h), with strongman (4.5-6.1 injuries per 1000 h) and Highland Games (7.5 injuries per 1000 h) reporting the highest rates. The shoulder, lower back, knee, elbow, and wrist/hand were generally the most commonly injured anatomical locations; strains, tendinitis, and sprains were the most common injury type. Very few significant differences in any of the injury outcomes were observed as a function of age, sex, competitive standard, or bodyweight class. While the majority of the research we reviewed utilized retrospective designs, the weight-training sports appear to have relatively low rates of injury compared with common team sports. Future weight-training sport injury epidemiology research needs to be improved, particularly in terms of the use of prospective designs, diagnosis of injury, and changes in risk exposure.

Statistical mechanics of competitive resource allocation using agent-based models

NASA Astrophysics Data System (ADS)

Chakraborti, Anirban; Challet, Damien; Chatterjee, Arnab; Marsili, Matteo; Zhang, Yi-Cheng; Chakrabarti, Bikas K.

2015-01-01

Demand outstrips available resources in most situations, which gives rise to competition, interaction and learning. In this article, we review a broad spectrum of multi-agent models of competition (El Farol Bar problem, Minority Game, Kolkata Paise Restaurant problem, Stable marriage problem, Parking space problem and others) and the methods used to understand them analytically. We emphasize the power of concepts and tools from statistical mechanics to understand and explain fully collective phenomena such as phase transitions and long memory, and the mapping between agent heterogeneity and physical disorder. As these methods can be applied to any large-scale model of competitive resource allocation made up of heterogeneous adaptive agent with non-linear interaction, they provide a prospective unifying paradigm for many scientific disciplines.

Modeling and simulating industrial land-use evolution in Shanghai, China

NASA Astrophysics Data System (ADS)

Qiu, Rongxu; Xu, Wei; Zhang, John; Staenz, Karl

2018-01-01

This study proposes a cellular automata-based Industrial and Residential Land Use Competition Model to simulate the dynamic spatial transformation of industrial land use in Shanghai, China. In the proposed model, land development activities in a city are delineated as competitions among different land-use types. The Hedonic Land Pricing Model is adopted to implement the competition framework. To improve simulation results, the Land Price Agglomeration Model was devised to simulate and adjust classic land price theory. A new evolutionary algorithm-based parameter estimation method was devised in place of traditional methods. Simulation results show that the proposed model closely resembles actual land transformation patterns and the model can not only simulate land development, but also redevelopment processes in metropolitan areas.

Competition for nutrients and light: testing advances in resource competition with a natural phytoplankton community.

PubMed

Burson, Amanda; Stomp, Maayke; Greenwell, Emma; Grosse, Julia; Huisman, Jef

2018-05-01

A key challenge in ecology is to understand how nutrients and light affect the biodiversity and community structure of phytoplankton and plant communities. According to resource competition models, ratios of limiting nutrients are major determinants of species composition. At high nutrient levels, however, species interactions may shift to competition for light, which might make nutrient ratios less relevant. The "nutrient-load hypothesis" merges these two perspectives, by extending the classic model of competition for two nutrients to include competition for light. Here, we test five key predictions of the nutrient-load hypothesis using multispecies competition experiments. A marine phytoplankton community sampled from the North Sea was inoculated in laboratory chemostats provided with different nitrogen (N) and phosphorus (P) loads to induce either single resource limitation or co-limitation of N, P, and light. Four of the five predictions were validated by the experiments. In particular, different resource limitations favored the dominance of different species. Increasing nutrient loads caused changes in phytoplankton species composition, even if the N:P ratio of the nutrient loads remained constant, by shifting the species interactions from competition for nutrients to competition for light. In all treatments, small species became dominant whereas larger species were competitively excluded, supporting the common view that small cell size provides a competitive advantage under resource-limited conditions. Contrary to expectation, all treatments led to coexistence of diatoms, cyanobacteria and green algae, resulting in a higher diversity of species than predicted by theory. Because the coexisting species comprised three phyla with different photosynthetic pigments, we speculate that niche differentiation in the light spectrum might play a role. Our results show that mechanistic resource competition models that integrate nutrient-based and light-based approaches provide an important step forward to understand and predict how changing nutrient loads affect community composition. © 2018 The Authors Ecology published by Wiley Periodicals, Inc. on behalf of Ecological Society of America.

The Resilient Economy: Integrating Competitiveness and Security

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debbie van Opstal

2009-01-07

Globalization, technological complexity, interdependence, terrorism, climate and energy volatility, and pandemic potential are increasing the level of risk that societies and organizations now face. Risks also are increasingly interrelated; disruptions in one area can cascade in multiple directions. The ability to manage emerging risks, anticipate the interactions between different types of risk, and bounce back from disruption will be a competitive differentiator for companies and countries alike in the 21st century. What Policymakers Should Know The national objective is not just homeland protection, but economic resilience: the ability to mitigate and recover quickly from disruption. Businesses must root the casemore » for investment in resilience strategies to manage a spectrum of risks, not just catastrophic ones. Making a business case for investment in defenses against low-probability events (even those with high impact) is difficult. However, making a business case for investments that assure business continuity and shareholder value is not a heavy lift. There are an infinite number of disruption scenarios, but only a finite number of outcomes. Leading organizations do not manage specific scenarios, rather they create the agility and flexibility to cope with turbulent situations. The investments and contingency plans these leading companies make to manage a spectrum of risk create a capability to respond to high-impact disasters as well. Government regulations tend to stovepipe different types of risk, which impedes companies abilities to manage risk in an integrated way. Policies to strengthen risk management capabilities would serve both security and competitiveness goals. What CEOs and Boards Should Know Operational risks are growing rapidly and outpacing many companies abilities to manage them. Corporate leadership has historically viewed operational risk management as a back office control function. But managing operational risks increasingly affects real-time financial performance. The 835 companies that announced a supply chain disruption between 1989 and 2000 experienced 33 percent to 40 percent lower stock returns than their industry peers. Twenty-five percent of companies that experienced an IT outage of two to six days went bankrupt immediately. Ninety-three percent of companies that lost their data center for 10 days or more filed for bankruptcy within a year.« less

Functional feeding traits as predictors of invasive success of alien freshwater fish species using a food-fish model.

PubMed

Nagelkerke, Leopold A J; van Onselen, Eline; van Kessel, Nils; Leuven, Rob S E W

2018-01-01

Invasions of Ponto-Caspian fish species into north-western European river basins accelerated since the opening of the Rhine-Main-Danube Canal in 1992. Since 2002, at least five Ponto-Caspian alien fish species have arrived in The Netherlands. Four species belong to the Gobiidae family (Neogobius fluviatilis, Neogobius melanostomus, Ponticola kessleri, and Proterorhinus semilunaris) and one to the Cyprinidae family (Romanogobio belingi). These species are expected to be potentially deleterious for the populations of four native benthic fish species: Gobio gobio (Cyprinidae), Barbatula barbatula (Nemacheilidae), Cottus perifretum, and C. rhenanus (Cottidae). Invasion success may be dependent on competitive trophic interactions with native species, which are enabled and/or constrained by feeding-related morphological traits. Twenty-two functional feeding traits were measured in nine species (in total 90 specimens). These traits were quantitatively linked to the mechanical, chemical and behavioral properties of a range of aquatic resource categories, using a previously developed food-fish model (FFM). The FFM was used to predict the trophic profile (TP) of each fish: the combined capacities to feed on each of the resource types. The most extreme TPs belonged to three alien species, indicating that they were most specialized among the studied species. Of these three, only P. kessleri overlapped with the two native Cottus species, indicating potential trophic competition. N. fluviatilis and R. belingi did not show any overlap, indicating that there is low trophic competition. The two remaining alien goby species (N. melanostomus and P. semilunaris) had average TPs and could be considered generalist feeders. They overlapped with each other and with G. gobio and B. barbatula, indicating potential trophic competition. This study suggests that both generalist and specialist species can be successful invaders. Since the FFM predicts potential interactions between species, it provides a tool to support horizon scanning and rapid risk assessments of alien species.

Consumer effects on the vital rates of their resource can determine the outcome of competition between consumers.

PubMed

Lee, Charlotte T; Miller, Tom E X; Inouye, Brian D

2011-10-01

Current competition theory does not adequately address the fact that competitors may affect the survival, growth, and reproductive rates of their resources. Ecologically important interactions in which consumers affect resource vital rates range from parasitism and herbivory to mutualism. We present a general model of competition that explicitly includes consumer-dependent resource vital rates. We build on the classic MacArthur model of competition for multiple resources, allowing direct comparison with expectations from established concepts of resource-use overlap. Consumers share a stage-structured resource population but may use the different stages to different extents, as they do the different independent resources in the classic model. Here, however, the stages are dynamically linked via consumer-dependent vital rates. We show that consumers' effects on resource vital rates result in two important departures from classic results. First, consumers can coexist despite identical use of resource stages, provided each competitor shifts the resource stage distribution toward stages that benefit other species. Second, consumers specializing on different resource stages can compete strongly, possibly resulting in competitive exclusion despite a lack of resource stage-use overlap. Our model framework demonstrates the critical role that consumer-dependent resource vital rates can play in competitive dynamics in a wide range of biological systems.

Modelling growth-competition relationships in trembling aspen and white spruce mixed boreal forests of Western Canada.

PubMed

Huang, Jian-Guo; Stadt, Kenneth J; Dawson, Andria; Comeau, Philip G

2013-01-01

We examined the effect of competition on stem growth of Picea glauca and Populus tremuloides in boreal mixedwood stands during the stem exclusion stage. We combined traditional approaches of collecting competition data with dendrochronology to provide retrospective measurements of stem diameter growth. Several competition indices including stand basal area (BA), the sum of stem diameter at breast height (SDBH), and density (N) for the broadleaf and coniferous species, as well as similar indices considering only trees with diameters greater than each subject (BAGR, SDBHGR, and NGR), were evaluated. We used a nonlinear mixed model to characterize the basal area increment over the past 5, 10, 15, 20, 25, 30, and 35 years as a function of growth of nearby dominant trees, the size of the subject trees, deciduous and coniferous competition indices, and ecoregions. SDBHGR and BAGR were better predictors for spruce, and SDBHGR and NGR were better for aspen, respectively, than other indices. Results showed strongest correlations with long-term stem growth, as the best models integrated growth for 10-25 years for aspen and ≥ 25 for spruce. Our model demonstrated a remarkable capability (adjusted R(2)>0.67) to represent this complex variation in growth as a function of site, size and competition.

Modelling Growth-Competition Relationships in Trembling Aspen and White Spruce Mixed Boreal Forests of Western Canada

PubMed Central

Huang, Jian-Guo; Stadt, Kenneth J.; Dawson, Andria; Comeau, Philip G.

2013-01-01

We examined the effect of competition on stem growth of Picea glauca and Populus tremuloides in boreal mixedwood stands during the stem exclusion stage. We combined traditional approaches of collecting competition data with dendrochronology to provide retrospective measurements of stem diameter growth. Several competition indices including stand basal area (BA), the sum of stem diameter at breast height (SDBH), and density (N) for the broadleaf and coniferous species, as well as similar indices considering only trees with diameters greater than each subject (BAGR, SDBHGR, and NGR), were evaluated. We used a nonlinear mixed model to characterize the basal area increment over the past 5, 10, 15, 20, 25, 30, and 35 years as a function of growth of nearby dominant trees, the size of the subject trees, deciduous and coniferous competition indices, and ecoregions. SDBHGR and BAGR were better predictors for spruce, and SDBHGR and NGR were better for aspen, respectively, than other indices. Results showed strongest correlations with long-term stem growth, as the best models integrated growth for 10–25 years for aspen and ≥25 for spruce. Our model demonstrated a remarkable capability (adjusted R2>0.67) to represent this complex variation in growth as a function of site, size and competition. PMID:24204891

Modelling the competition of planktonic and sessile aerobic heterotrophs for complementary nutrients in biofilm reactor.

PubMed

Lu, T; Saikaly, P E; Oerther, D B

2007-01-01

A comprehensive, simplified microbial biofilm model was developed to evaluate the impact of bioreactor operating parameters on changes in microbial population abundance. Biofilm simulations were conducted using three special cases: fully penetrated, internal mass transfer resistance and external mass transfer resistance. The results of model simulations showed that for certain operating conditions, competition for growth limiting nutrients generated oscillations in the abundance of planktonic and sessile microbial populations. These oscillations resulted in the violation of the competitive exclusion principle where the number of microbial populations was greater than the number of growth limiting nutrients. However, the operating conditions which impacted microbial community diversity were different for the three special cases. Comparing the results of model simulations for dispersed-growth, biofilms and bioflocs showed that oscillations and microbial community diversity were a function of competition as well as other key features of the ecosystem. The significance of the current study is that it is the first to examine competition as a mechanism for controlling microbial community diversity in biofilm reactors.

Role of intraspecific competition in the coexistence of mobile populations in spatially extended ecosystems.

PubMed

Yang, Rui; Wang, Wen-Xu; Lai, Ying-Cheng; Grebogi, Celso

2010-06-01

Evolutionary-game based models of nonhierarchical, cyclically competing populations have become paradigmatic for addressing the fundamental problem of species coexistence in spatially extended ecosystems. We study the role of intraspecific competition in the coexistence and find that the competition can strongly promote the coexistence for high individual mobility in the sense that stable coexistence can arise in parameter regime where extinction would occur without the competition. The critical value of the competition rate beyond which the coexistence is induced is found to be independent of the mobility. We derive a theoretical model based on nonlinear partial differential equations to predict the critical competition rate and the boundaries between the coexistence and extinction regions in a relevant parameter space. We also investigate pattern formation and well-mixed spatiotemporal population dynamics to gain further insights into our findings. (c) 2010 American Institute of Physics.

Competition both drives and impedes diversification in a model adaptive radiation

PubMed Central

Bailey, Susan F.; Dettman, Jeremy R.; Rainey, Paul B.; Kassen, Rees

2013-01-01

Competitors are known to be important in governing the outcome of evolutionary diversification during an adaptive radiation, but the precise mechanisms by which they exert their effects remain elusive. Using the model adaptive radiation of Pseudomonas fluorescens, we show experimentally that the effect of competition on diversification of a focal lineage depends on both the strength of competition and the ability of the competitors to diversify. We provide evidence that the extent of diversification in the absence of interspecific competitors depends on the strength of resource competition. We also show that the presence of competitors can actually increase diversity by increasing interspecific resource competition. Competitors that themselves are able to diversify prevent diversification of the focal lineage by removing otherwise available ecological opportunities. These results suggest that the progress of an adaptive radiation depends ultimately on the strength of resource competition, an effect that can be exaggerated or impeded by the presence of competitors. PMID:23843392

Determinants of choice, and vulnerability and recovery in addiction.

PubMed

Lamb, R J; Maguire, David R; Ginsburg, Brett C; Pinkston, Jonathan W; France, Charles P

2016-06-01

Addiction may be viewed as choice governed by competing contingencies. One factor impacting choice, particularly as it relates to addiction, is sensitivity to delayed rewards. Discounting of delayed rewards influences addiction vulnerability because of competition between relatively immediate gains of drug use, e.g. intoxication, versus relatively remote gains of abstinence, e.g. family stability. Factors modifying delay sensitivity can be modeled in the laboratory. For instance, increased delay sensitivity can be similarly observed in adolescent humans and non-human animals. Similarly, genetic factors influence delay sensitivity in humans and animals. Recovery from addiction may also be viewed as choice behavior. Thus, reinforcing alternative behavior facilitates recovery because reinforcing alternative behavior decreases the frequency of using drugs. How reinforcing alternative behavior influences recovery can also be modeled in the laboratory. For instance, relapse risk decreases as abstinence duration increases, and this decreasing risk can be modeled in animals using choice procedures. In summary, addiction in many respects can be conceptualized as a problem of choice. Animal models of choice disorders stand to increase our understanding of the core processes that establish and maintain addiction and serve as a proving ground for development of novel treatments. Copyright © 2016 Elsevier B.V. All rights reserved.

Determinants of choice, and vulnerability and recovery in addiction

PubMed Central

Lamb, R.J.; Maguire, David R.; Ginsburg, Brett C.; Pinkston, Jonathan W.; France, Charles P.

2016-01-01

Addiction may be viewed as choice governed by competing contingencies. One factor impacting choice, particularly as it relates to addiction, is sensitivity to delayed rewards. Discounting of delayed rewards influences addiction vulnerability because of competition between relatively immediate gains of drug use, e.g. intoxication, versus relatively remote gains of abstinence, e.g. family stability. Factors modifying delay sensitivity can be modeled in the laboratory. For instance, increased delay sensitivity can be similarly observed in adolescent humans and non-human animals. Similarly, genetic factors influence delay sensitivity in humans and animals. Recovery from addiction may also be viewed as choice behavior. Thus, reinforcing alternative behavior facilitates recovery because reinforcing alternative behavior decreases the frequency of using drugs. How reinforcing alternative behavior influences recovery can also be modeled in the laboratory. For instance, relapse risk decreases as abstinence duration increases, and this decreasing risk can be modeled in animals using choice procedures. In summary, addiction in many respects can be conceptualized as a problem of choice. Animal models of choice disorders stand to increase our understanding of the core processes that establish and maintain addiction and serve as a proving ground for development of novel treatments. PMID:27083500

Competitive Electricity Market Regulation in the United States: A Primer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flores-Espino, Francisco; Tian, Tian; Chernyakhovskiy, Ilya

The electricity system in the United States is a complex mechanism where different technologies, jurisdictions and regulatory designs interact. Today, two major models for electricity commercialization operate in the United States. One is the regulated monopoly model, in which vertically integrated electricity providers are regulated by state commissions. The other is the competitive model, in which power producers can openly access transmission infrastructure and participate in wholesale electricity markets. This paper describes the origins, evolution, and current status of the regulations that enable competitive markets in the United States.

Hip Strength as a Predictor of Ankle Sprains in Male Soccer Players: A Prospective Study.

PubMed

Powers, Christopher M; Ghoddosi, Navid; Straub, Rachel K; Khayambashi, Khalil

2017-11-01

  Diminished hip-abductor strength has been suggested to increase the risk of noncontact lateral ankle sprains.   To determine prospectively whether baseline hip-abductor strength predicts future noncontact lateral ankle sprains in competitive male soccer players.   Prospective cohort study.   Athletic training facilities and various athletic fields.   Two hundred ten competitive male soccer players.   Before the start of the sport season, isometric hip-abductor strength was measured bilaterally using a handheld dynamometer. Any previous history of ankle sprain, body mass index, age, height, and weight were documented. During the sport season (30 weeks), ankle injury status was recorded by team medical providers. Injured athletes were further classified based on the mechanism of injury. Only data from injured athletes who sustained noncontact lateral ankle sprains were used for analysis. Postseason, logistic regression was used to determine whether baseline hip strength predicted future noncontact lateral ankle sprains. A receiver operating characteristic curve was constructed for hip strength to determine the cutoff value for distinguishing between high-risk and low-risk outcomes.   A total of 25 noncontact lateral ankle sprains were confirmed, for an overall annual incidence of 11.9%. Baseline hip-abductor strength was lower in injured players than in uninjured players ( P = .008). Logistic regression indicated that impaired hip-abductor strength increased the future injury risk (odds ratio = 1.10 [95% confidence interval = 1.02, 1.18], P = .010). The strength cutoff to define high risk was ≤33.8% body weight, as determined by receiver operating characteristic curve analysis. For athletes classified as high risk, the probability of injury increased from 11.9% to 26.7%.   Reduced isometric hip-abductor strength predisposed competitive male soccer players to noncontact lateral ankle sprains.

Effect of Regional Hospital Competition and Hospital Financial Status on the Use of Robotic-Assisted Surgery.

PubMed

Wright, Jason D; Tergas, Ana I; Hou, June Y; Burke, William M; Chen, Ling; Hu, Jim C; Neugut, Alfred I; Ananth, Cande V; Hershman, Dawn L

2016-07-01

Despite the lack of efficacy data, robotic-assisted surgery has diffused rapidly into practice. Marketing to physicians, hospitals, and patients has been widespread, but how this marketing has contributed to the diffusion of the technology remains unknown. To examine the effect of regional hospital competition and hospital financial status on the use of robotic-assisted surgery for 5 commonly performed procedures. A cohort study of 221 637 patients who underwent radical prostatectomy, total nephrectomy, partial nephrectomy, hysterectomy, or oophorectomy at 1370 hospitals in the United States from January 1, 2010, to December 31, 2011, was conducted. The association between hospital competition, hospital financial status, and performance of robotic-assisted surgery was examined. The association between hospital competition was measured with the Herfindahl-Hirschman Index (HHI), hospital financial status was estimated as operating margin, and performance of robotic-assisted surgery was examined using multivariate mixed-effects regression models. We identified 221 637 patients who underwent one of the procedures of interest. The cohort included 30 345 patients who underwent radical prostatectomy; 20 802, total nephrectomy; 8060, partial nephrectomy; 134 985, hysterectomy; and 27 445, oophorectomy. Robotic-assisted operations were performed for 20 500 (67.6%) radical prostatectomies, 1405 (6.8%) total nephrectomies, 2759 (34.2%) partial nephrectomies, 14 047 (10.4%) hysterectomies, and 1782 (6.5%) oophorectomies. Use of robotic-assisted surgery increased for each procedure from January 2010 through December 2011. For all 5 operations, increased market competition (as measured by the HHI) was associated with increased use of robotic-assisted surgery. For prostatectomy, the risk ratios (95% CIs) for undergoing a robotic-assisted procedure were 2.20 (1.50-3.24) at hospitals in moderately competitive markets and 2.64 (1.84-3.78) for highly competitive markets compared with noncompetitive markets. For hysterectomy, patients at hospitals in moderately (3.75 [2.26-6.25]) and highly (5.30; [3.27-8.57]) competitive markets were more likely to undergo a robotic-assisted surgery. Increased hospital profitability was associated with use of robotic-assisted surgery only for partial nephrectomy in facilities with medium-high (1.67 [1.13-2.48]) and high (1.50 [0.98-2.29]) operating margins. With analysis limited to patients treated at a hospital that had performed robotic-assisted surgery, there was no longer an association between competition and use of robotic-assisted surgery. Patients undergoing surgery in a hospital in a competitive regional market were more likely to undergo a robotic-assisted procedure. These data imply that regional competition may influence a hospital's decision to acquire a surgical robot.

The Integrated Airport Competition Model, 1998

NASA Technical Reports Server (NTRS)

Veldhuis, J.; Essers, I.; Bakker, D.; Cohn, N.; Kroes, E.

1999-01-01

This paper addresses recent model development by the Directorate General of Civil Aviation (DGCA) and Hague Consulting Group (HCG) concerning long-distance travel, Long-distance travel demand is growing very quickly and raising a great deal of economic and policy issues. There is increasing competition among the main Western European airports, and smaller, regional airports are fighting for market share. New modes of transport, such as high speed rail, arc also coming into the picture and affect the mode split for medium distance transport within Europe. Developments such as these are demanding the attention of policy makers and a tool is required for their analysis. For DGCA, Hague Consulting Group has developed a model system to provide answers to the policy questions posed by these expected trends, and to identify areas where policy makers can influence the traveller choices. The development of this model system, the Integrated Airport Competition Model/Integral Luchthaven Competitive Model (ILCM), began in 1992. Since that time the sub-models, input data and user interface have been expanded, updated and improved. HCG and DGCA have transformed the ILCM from a prototype into an operational forecasting tool.

Modeling of the Competitive Growth of Listeria monocytogenes and Lactococcus lactis in Vegetable Broth

PubMed Central

Breidt, Frederick; Fleming, Henry P.

1998-01-01

Current mathematical models used by food microbiologists do not address the issue of competitive growth in mixed cultures of bacteria. We developed a mathematical model which consists of a system of nonlinear differential equations describing the growth of competing bacterial cell cultures. In this model, bacterial cell growth is limited by the accumulation of protonated lactic acid and decreasing pH. In our experimental system, pure and mixed cultures of Lactococcus lactis and Listeria monocytogenes were grown in a vegetable broth medium. Predictions of the model indicate that pH is the primary factor that limits the growth of L. monocytogenes in competition with a strain of L. lactis which does not produce the bacteriocin nisin. The model also predicts the values of parameters that affect the growth and death of the competing populations. Further development of this model will incorporate the effects of additional inhibitors, such as bacteriocins, and may aid in the selection of lactic acid bacterium cultures for use in competitive inhibition of pathogens in minimally processed foods. PMID:9726854

The contribution of competition to tree mortality in old-growth coniferous forests

USGS Publications Warehouse

Das, A.; Battles, J.; Stephenson, N.L.; van Mantgem, P.J.

2011-01-01

Competition is a well-documented contributor to tree mortality in temperate forests, with numerous studies documenting a relationship between tree death and the competitive environment. Models frequently rely on competition as the only non-random mechanism affecting tree mortality. However, for mature forests, competition may cease to be the primary driver of mortality.We use a large, long-term dataset to study the importance of competition in determining tree mortality in old-growth forests on the western slope of the Sierra Nevada of California, U.S.A. We make use of the comparative spatial configuration of dead and live trees, changes in tree spatial pattern through time, and field assessments of contributors to an individual tree's death to quantify competitive effects.Competition was apparently a significant contributor to tree mortality in these forests. Trees that died tended to be in more competitive environments than trees that survived, and suppression frequently appeared as a factor contributing to mortality. On the other hand, based on spatial pattern analyses, only three of 14 plots demonstrated compelling evidence that competition was dominating mortality. Most of the rest of the plots fell within the expectation for random mortality, and three fit neither the random nor the competition model. These results suggest that while competition is often playing a significant role in tree mortality processes in these forests it only infrequently governs those processes. In addition, the field assessments indicated a substantial presence of biotic mortality agents in trees that died.While competition is almost certainly important, demographics in these forests cannot accurately be characterized without a better grasp of other mortality processes. In particular, we likely need a better understanding of biotic agents and their interactions with one another and with competition. ?? 2011.

Impact of competitive flow on wall shear stress in coronary surgery: computational fluid dynamics of a LIMA-LAD model.

PubMed

Nordgaard, Håvard; Swillens, Abigail; Nordhaug, Dag; Kirkeby-Garstad, Idar; Van Loo, Denis; Vitale, Nicola; Segers, Patrick; Haaverstad, Rune; Lovstakken, Lasse

2010-12-01

Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts. Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, <0.05, and <0.05, respectively. Thus, high competitive flow resulted in substantial oscillatory and low WSS. Moderate competitive flow resulted in WSS and OSI similar to the no competitive flow condition. Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

Punishment in human choice: direct or competitive suppression?

PubMed Central

Critchfield, Thomas S; Paletz, Elliott M; MacAleese, Kenneth R; Newland, M Christopher

2003-01-01

This investigation compared the predictions of two models describing the integration of reinforcement and punishment effects in operant choice. Deluty's (1976) competitive-suppression model (conceptually related to two-factor punishment theories) and de Villiers' (1980) direct-suppression model (conceptually related to one-factor punishment theories) have been tested previously in nonhumans but not at the individual level in humans. Mouse clicking by college students was maintained in a two-alternative concurrent schedule of variable-interval money reinforcement. Punishment consisted of variable-interval money losses. Experiment 1 verified that money loss was an effective punisher in this context. Experiment 2 consisted of qualitative model comparisons similar to those used in previous studies involving nonhumans. Following a no-punishment baseline, punishment was superimposed upon both response alternatives. Under schedule values for which the direct-suppression model, but not the competitive-suppression model, predicted distinct shifts from baseline performance, or vice versa, 12 of 14 individual-subject functions, generated by 7 subjects, supported the direct-suppression model. When the punishment models were converted to the form of the generalized matching law, least-squares linear regression fits for a direct-suppression model were superior to those of a competitive-suppression model for 6 of 7 subjects. In Experiment 3, a more thorough quantitative test of the modified models, fits for a direct-suppression model were superior in 11 of 13 cases. These results correspond well to those of investigations conducted with nonhumans and provide the first individual-subject evidence that a direct-suppression model, evaluated both qualitatively and quantitatively, describes human punishment better than a competitive-suppression model. We discuss implications for developing better punishment models and future investigations of punishment in human choice. PMID:13677606

Disentangling Decision Models: From Independence to Competition

ERIC Educational Resources Information Center

Teodorescu, Andrei R.; Usher, Marius

2013-01-01

A multitude of models have been proposed to account for the neural mechanism of value integration and decision making in speeded decision tasks. While most of these models account for existing data, they largely disagree on a fundamental characteristic of the choice mechanism: independent versus different types of competitive processing. Five…

Cost modeling of pseudomonoas fluorescens and pseudomonoas chlororphis biocontrol for competitive exclusion of salmonella enterica on tomatoes

USDA-ARS?s Scientific Manuscript database

Biocontrol measures may enhance postharvest interventions, however; published research on process-based models for biocontrol of foodborne pathogens on produce is limited. The aim of this research was to develop cost model estimates for competitive exclusion process using Pseudomonas fluorescens and...

Incidence of injury in professional mixed martial arts competitions.

PubMed

Bledsoe, Gregory H; Hsu, Edbert B; Grabowski, Jurek George; Brill, Justin D; Li, Guohua

2006-01-01

Mixed Martial Arts (MMA) competitions were introduced in the United States with the first Ultimate Fighting Championship (UFC) in 1993. In 2001, Nevada and New Jersey sanctioned MMA events after requiring a series of rule changes. The purpose of this study was to determine the incidence of injury in professional MMA fighters. Data from all professional MMA events that took place between September 2001 and December 2004 in the state of Nevada were obtained from the Nevada Athletic Commission. Medical and outcome data from events were analyzed based on a pair-matched case-control design. Both conditional and unconditional logistic regression models were used to assess risk factors for injury. A total of 171 MMA matches involving 220 different fighters occurred during the study period. There were a total of 96 injuries to 78 fighters. Of the 171 matches fought, 69 (40.3%) ended with at least one injured fighter. The overall injury rate was 28.6 injuries per 100 fight participations or 12.5 injuries per 100 competitor rounds. Facial laceration was the most common injury accounting for 47.9% of all injuries, followed by hand injury (13.5%), nose injury (10.4%), and eye injury (8.3%). With adjustment for weight and match outcome, older age was associated with significantly increased risk of injury. The most common conclusion to a MMA fight was a technical knockout (TKO) followed by a tap out. The injury rate in MMA competitions is compatible with other combat sports involving striking. The lower knockout rates in MMA compared to boxing may help prevent brain injury in MMA events. Key PointsMixed martial arts (MMA) has changed since the first MMA matches in the United States and now has increased safety regulations and sanctioning.MMA competitions have an overall high rate of injury.There have been no MMA deaths in the United States.The knockout (KO) rate in MMA appears to be lower than the KO rate of boxing matches.MMA must continue to be supervised by properly trained medical professionals and referees to ensure fighter safety in the future.

Incidence of Injury in Professional Mixed Martial Arts Competitions

PubMed Central

Bledsoe, Gregory H.; Hsu, Edbert B.; Grabowski, Jurek George; Brill, Justin D.; Li, Guohua

2006-01-01

Mixed Martial Arts (MMA) competitions were introduced in the United States with the first Ultimate Fighting Championship (UFC) in 1993. In 2001, Nevada and New Jersey sanctioned MMA events after requiring a series of rule changes. The purpose of this study was to determine the incidence of injury in professional MMA fighters. Data from all professional MMA events that took place between September 2001 and December 2004 in the state of Nevada were obtained from the Nevada Athletic Commission. Medical and outcome data from events were analyzed based on a pair-matched case-control design. Both conditional and unconditional logistic regression models were used to assess risk factors for injury. A total of 171 MMA matches involving 220 different fighters occurred during the study period. There were a total of 96 injuries to 78 fighters. Of the 171 matches fought, 69 (40.3%) ended with at least one injured fighter. The overall injury rate was 28.6 injuries per 100 fight participations or 12.5 injuries per 100 competitor rounds. Facial laceration was the most common injury accounting for 47.9% of all injuries, followed by hand injury (13.5%), nose injury (10.4%), and eye injury (8.3%). With adjustment for weight and match outcome, older age was associated with significantly increased risk of injury. The most common conclusion to a MMA fight was a technical knockout (TKO) followed by a tap out. The injury rate in MMA competitions is compatible with other combat sports involving striking. The lower knockout rates in MMA compared to boxing may help prevent brain injury in MMA events. Key Points Mixed martial arts (MMA) has changed since the first MMA matches in the United States and now has increased safety regulations and sanctioning. MMA competitions have an overall high rate of injury. There have been no MMA deaths in the United States. The knockout (KO) rate in MMA appears to be lower than the KO rate of boxing matches. MMA must continue to be supervised by properly trained medical professionals and referees to ensure fighter safety in the future. PMID:24357986

Magnitude and Mechanism of Siderophore-Mediated Competition at Low Iron Solubility in the Pseudomonas aeruginosa Pyochelin System.

PubMed

Schiessl, Konstanze T; Janssen, Elisabeth M-L; Kraemer, Stephan M; McNeill, Kristopher; Ackermann, Martin

2017-01-01

A central question in microbial ecology is whether microbial interactions are predominantly cooperative or competitive. The secretion of siderophores, microbial iron chelators, is a model system for cooperative interactions. However, siderophores have also been shown to mediate competition by sequestering available iron and making it unavailable to competitors. The details of how siderophores mediate competition are not well understood, especially considering the complex distribution of iron phases in the environment. One pertinent question is whether sequestering iron through siderophores can indeed be effective in natural conditions; many natural environments are characterized by large pools of precipitated iron, and it is conceivable that any soluble iron that is sequestered by siderophores is replenished by the dissolution of these precipitated iron sources. Our goal here was to address this issue, and investigate the magnitude and mechanism of siderophore-mediated competition in the presence of precipitated iron. We combined experimental work with thermodynamic modeling, using Pseudomonas aeruginosa as a model system and ferrihydrite precipitates as the iron source with low solubility. Our experiments show that competitive growth inhibition by the siderophore pyochelin is indeed efficient, and that inhibition of a competitor can even have a stronger growth-promoting effect than solubilization of precipitated iron. Based on the results of our thermodynamic models we conclude that the observed inhibition of a competitor is effective because sequestered iron is only very slowly replenished by the dissolution of precipitated iron. Our research highlights the importance of competitive benefits mediated by siderophores, and underlines that the dynamics of siderophore production and uptake in environmental communities could be a signature of competitive, not just cooperative, dynamics.

The Work Ahead.

ERIC Educational Resources Information Center

Hess, Frederick M.

2001-01-01

Argues that public schools must change their underlying culture and rules to benefit from competition from charter schools and voucher programs. Discusses differences between educational marketplace and traditional economic models, finding schools less responsive to competitive pressures. Analyzes factors constraining competition and offers…

The need of a weight management control program in judo: a proposal based on the successful case of wrestling.

PubMed

Artioli, Guilherme G; Franchini, Emerson; Nicastro, Humberto; Sterkowicz, Stanislaw; Solis, Marina Y; Lancha, Antonio H

2010-05-04

Judo competitions are divided into weight classes. However, most athletes reduce their body weight in a few days before competition in order to obtain a competitive advantage over lighter opponents. To achieve fast weight reduction, athletes use a number of aggressive nutritional strategies so many of them place themselves at a high health-injury risk. In collegiate wrestling, a similar problem has been observed and three wrestlers died in 1997 due to rapid weight loss regimes. After these deaths, the National Collegiate Athletic Association had implemented a successful weight management program which was proven to improve weight management behavior. No similar program has ever been discussed by judo federations even though judo competitors present a comparable inappropriate pattern of weight control. In view of this, the basis for a weight control program is provided in this manuscript, as follows: competition should begin within 1 hour after weigh-in, at the latest; each athlete is allowed to be weighed-in only once; rapid weight loss as well as artificial rehydration (i.e., saline infusion) methods are prohibited during the entire competition day; athletes should pass the hydration test to get their weigh-in validated; an individual minimum competitive weight (male athletes competing at no less than 7% and females at no less than 12% of body fat) should be determined at the beginning of each season; athletes are not allowed to compete in any weight class that requires weight reductions greater than 1.5% of body weight per week. In parallel, educational programs should aim at increasing the athletes', coaches' and parents' awareness about the risks of aggressive nutritional strategies as well as healthier ways to properly manage body weight.

Low Risk of Injuries in Young Adolescents Participating in Top-Level Karate Competition.

PubMed

Arriaza, Rafael; Inman, David; Arriaza, Alvaro; Saavedra, Miguel A

2016-02-01

Prospective studies on injuries in martial arts competition are scarce, especially those involving young practitioners, but the upsurge of children and adolescents taking part in organized training and competition in these sports requires clarification of the injury risk that they represent for youths. Top-level karate competition for young adolescents (cadets, or 14- to 15-year-olds) has a low injury rate and can be safely promoted. Descriptive epidemiological study. Prospective recording of the injuries resulting from all bouts in 3 consecutive World Karate Championships (2009, 2011, and 2013) for cadets was performed. Data were collected prospectively in situ with checklists that described competitor sex, bout category, and weight as well as injured area, diagnosis, mechanism of injury, severity, and treatment. A total of 1020 bouts were reviewed, 671 in the male category and 349 in the female category. A total of 61 injuries were recorded. Of those, only 3 were time-loss injuries. During the 2009 and 2011 championships, there was 1 injury per 25.6 fights, while during the 2013 championship the number of injuries increased, with 1 injury per 10 fights (P = .003). There was no statistical difference in the total injury rate between the male and female categories (P = .71), with an odds ratio of 1.16 (95% CI, 0.52-2.55). The injury rate for cadet top-level karate competition found in this prospective study is much lower than the rates previously published for karate or other martial arts competitions, but there seems to be a marked increase as more championships are held, which is a matter of concern. © 2015 The Author(s).

A General Model of Distant Hybridization Reveals the Conditions for Extinction in Atlantic Salmon and Brown Trout

PubMed Central

Quilodrán, Claudio S.; Currat, Mathias; Montoya-Burgos, Juan I.

2014-01-01

Interspecific hybridization is common in nature but can be increased in frequency or even originated by human actions, such as species introduction or habitat modification, which may threaten species persistence. When hybridization occurs between distantly related species, referred to as “distant hybridization,” the resulting hybrids are generally infertile or fertile but do not undergo chromosomal recombination during gametogenesis. Here, we present a model describing this frequent but poorly studied interspecific hybridization to assess its consequences on parental species and to anticipate the conditions under which they can reach extinction. Our general model fully incorporates three important processes: density-dependent competition, dominance/recessivity inheritance of traits and assortative mating. We demonstrate its use and flexibility by assessing population extinction risk between Atlantic salmon and brown trout in Norway, whose interbreeding has recently increased due to farmed fish releases into the wild. We identified the set of conditions under which hybridization may threaten salmonid species. Thanks to the flexibility of our model, we evaluated the effect of an additional risk factor, a parasitic disease, and showed that the cumulative effects dramatically increase the extinction risk. The consequences of distant hybridization are not genetically, but demographically mediated. Our general model is useful to better comprehend the evolution of such hybrid systems and we demonstrated its importance in the field of conservation biology to set up management recommendations when this increasingly frequent type of hybridization is in action. PMID:25003336

A general model of distant hybridization reveals the conditions for extinction in Atlantic salmon and brown trout.

PubMed

Quilodrán, Claudio S; Currat, Mathias; Montoya-Burgos, Juan I

2014-01-01

Interspecific hybridization is common in nature but can be increased in frequency or even originated by human actions, such as species introduction or habitat modification, which may threaten species persistence. When hybridization occurs between distantly related species, referred to as "distant hybridization," the resulting hybrids are generally infertile or fertile but do not undergo chromosomal recombination during gametogenesis. Here, we present a model describing this frequent but poorly studied interspecific hybridization to assess its consequences on parental species and to anticipate the conditions under which they can reach extinction. Our general model fully incorporates three important processes: density-dependent competition, dominance/recessivity inheritance of traits and assortative mating. We demonstrate its use and flexibility by assessing population extinction risk between Atlantic salmon and brown trout in Norway, whose interbreeding has recently increased due to farmed fish releases into the wild. We identified the set of conditions under which hybridization may threaten salmonid species. Thanks to the flexibility of our model, we evaluated the effect of an additional risk factor, a parasitic disease, and showed that the cumulative effects dramatically increase the extinction risk. The consequences of distant hybridization are not genetically, but demographically mediated. Our general model is useful to better comprehend the evolution of such hybrid systems and we demonstrated its importance in the field of conservation biology to set up management recommendations when this increasingly frequent type of hybridization is in action.

Competitive release and outbreaks of non-target pests associated with transgenic Bt cotton.

PubMed

Zeilinger, Adam R; Olson, Dawn M; Andow, David A

2016-06-01

The adoption of transgenic Bt cotton has, in some cases, led to environmental and economic benefits through reduced insecticide use. However, the distribution of these benefits and associated risks among cotton growers and cotton-growing regions has been uneven due in part to outbreaks of non-target or secondary pests, thereby requiring the continued use of synthetic insecticides. In the southeastern USA, Bt cotton adoption has resulted in increased abundance of and damage from stink bug pests, Euschistus servus and Nezara viridula (Heteroptera: Pentatomidae). While the impact of increased stink bug abundance has been well-documented, the causes have remained unclear. We hypothesize that release from competition with Bt-susceptible target pests may drive stink bug outbreaks in Bt cotton. We first examined the evidence for competitive release of stink bugs through meta-analysis of previous studies. We then experimentally tested if herbivory by Bt-susceptible Helicoverpa zea increases stink bug leaving rates and deters oviposition on non-Bt cotton. Consistent with previous studies, we found differences in leaving rates only for E servus, but we found that both species strongly avoided ovipositing on H. zea-damaged plants. Considering all available evidence, competitive release of stink bug populations in Bt cotton likely contributes to outbreaks, though the relative importance of competitive release remains an open question. Ecological risk assessments of Bt crops and other transgenic insecticidal crops would benefit from greater understanding of the ecological mechanisms underlying non-target pest outbreaks and greater attention to indirect ecological effects more broadly.

Tactic-specific differences in seminal fluid influence sperm performance

PubMed Central

Locatello, Lisa; Poli, Federica; Rasotto, Maria B.

2013-01-01

Seminal fluid often makes up a large part of an ejaculate, yet most empirical and theoretical studies on sperm competition have focused on how sperm characteristics (number and quality) affect fertilization success. However, seminal fluid influences own sperm performance and may potentially influence the outcome of sperm competition, by also affecting that of rivals. As a consequence males may be expected to allocate their investment in both sperm and seminal fluid in relation to the potential level of competition. Grass goby (Zosterisessor ophiocephalus) is an external fertilizer with guard-sneaker mating tactics, where sperm competition risk varies according to the tactic adopted. Here, we experimentally manipulated grass goby ejaculates by separately combining sperm and seminal fluid from territorial and sneaker males. While sperm of sneaker and territorial males did not differ in their performance when they interacted with their own seminal fluid only, sperm of sneakers increased their velocity and fertilization rate in the presence of territorial males' seminal fluid. By contrast, sneaker males' seminal fluid had a detrimental effect on the performance of territorial males' sperm. Sperm velocity was unaffected by the seminal fluid of males employing the same tactic, suggesting that seminal fluid's effect on rival-tactic sperm is not based on a self/non-self recognition mechanism. Our findings show that cross interactions of sperm and seminal fluid may influence the fertilization success of competing ejaculates with males investing in both sperm and seminal fluid in response to sperm competition risk. PMID:23363633

Tactic-specific differences in seminal fluid influence sperm performance.

PubMed

Locatello, Lisa; Poli, Federica; Rasotto, Maria B

2013-03-22

Seminal fluid often makes up a large part of an ejaculate, yet most empirical and theoretical studies on sperm competition have focused on how sperm characteristics (number and quality) affect fertilization success. However, seminal fluid influences own sperm performance and may potentially influence the outcome of sperm competition, by also affecting that of rivals. As a consequence males may be expected to allocate their investment in both sperm and seminal fluid in relation to the potential level of competition. Grass goby (Zosterisessor ophiocephalus) is an external fertilizer with guard-sneaker mating tactics, where sperm competition risk varies according to the tactic adopted. Here, we experimentally manipulated grass goby ejaculates by separately combining sperm and seminal fluid from territorial and sneaker males. While sperm of sneaker and territorial males did not differ in their performance when they interacted with their own seminal fluid only, sperm of sneakers increased their velocity and fertilization rate in the presence of territorial males' seminal fluid. By contrast, sneaker males' seminal fluid had a detrimental effect on the performance of territorial males' sperm. Sperm velocity was unaffected by the seminal fluid of males employing the same tactic, suggesting that seminal fluid's effect on rival-tactic sperm is not based on a self/non-self recognition mechanism. Our findings show that cross interactions of sperm and seminal fluid may influence the fertilization success of competing ejaculates with males investing in both sperm and seminal fluid in response to sperm competition risk.

Context dependence of acorn handling by the Algerian mouse (Mus spretus)

NASA Astrophysics Data System (ADS)

Gallego, D.; Morán-López, T.; Torre, I.; Navarro-Castilla, Á.; Barja, I.; Díaz, M.

2017-10-01

Perceived predation risk and competition for acorns are expected to affect scatter-hoarding decisions by Algerian mice (Mus spretus). We manipulated both factors by means of predator fecal scents and ungulate exclosures. We hypothesized that high-risk perception and ungulate presence would promote acorn dispersal. In the former case, it would stimulate acorn mobilization to safe microhabitats rather than in situ consumption. In the latter, increased competition for acorns would promote their storage for later consumption. We also expected that mice would adapt their foraging behavior to previous experience modulating the strength of these effects. In the presence of ungulates, mice focused their foraging activities on food acquisition at the expenses of vigilant behaviors. However, a more efficient foraging did not entail enhanced dispersal services. Lack of anti-predatory cover in tree surroundings may have deterred mice from transporting seeds outside canopies. Increased risk interacted with previous experience. In control trees (no predator odor), mice confidence increased throughout the night resulting in decreased vigilance and enhanced acorn mobilization rates. In contrast, in risky conditions (trees with predator odor) mice maintained a base-line vigilant behavior. Contrary to our expectations, increased risk did not result in higher acorn mobilization, but the opposite. Again, the scarcity of safe microhabitats for mobilization may have been the underlying cause of this behavior. Our results show that successful acorn dispersal depends, at least partly, on plant-animal relationships that are beyond the oak-rodent mutualism. Thus, any conservation policy aimed at restoring natural regeneration of oaks should take into account the interaction network in which oak-rodent encounters are embedded. In addition, they suggest that mice incorporate direct and indirect cues of risks (habitat structure) through recent experience. A better understanding of this process will improve our ability to incorporate such temporal and spatial variability in models of acorn dispersal.

Terminal spacecraft rendezvous and capture with LASSO model predictive control

NASA Astrophysics Data System (ADS)

Hartley, Edward N.; Gallieri, Marco; Maciejowski, Jan M.

2013-11-01

The recently investigated ℓasso model predictive control (MPC) is applied to the terminal phase of a spacecraft rendezvous and capture mission. The interaction between the cost function and the treatment of minimum impulse bit is also investigated. The propellant consumption with ℓasso MPC for the considered scenario is noticeably less than with a conventional quadratic cost and control actions are sparser in time. Propellant consumption and sparsity are competitive with those achieved using a zone-based ℓ1 cost function, whilst requiring fewer decision variables in the optimisation problem than the latter. The ℓasso MPC is demonstrated to meet tighter specifications on control precision and also avoids the risk of undesirable behaviours often associated with pure ℓ1 stage costs.

Brief communication: the ecosystem perspective in ecotoxicology as a way forward for the ecological risk assessment of chemicals.

PubMed

De Laender, Frederik; Janssen, Colin R

2013-07-01

One of the objectives of the European Union (EU) ecological risk assessment of chemicals (ERA) is to derive maximum environmental concentrations that are not expected to cause adverse ecological effects. To this end, related EU directives list protection goals as well as guidelines that should be used to reach these goals. It is generally accepted that the individual-level endpoints on which these guidelines are based do not correspond to the listed population- and ecosystem-level protection goals. In this article, we identify 5 research topics that are key to bridging this gap: 1) the refinement of population-level effects and recovery rates by explicitly taking into account competition and 2) predation, 3) the assessment of chemical effects on biodiversity, 4) the assessment of chemical stress on ecosystem functions and services, and 5) the quantification of the effects of chemical mixtures. In addition, we illustrate why an ecosystem perspective is needed to address these topics and to inform the risk assessment process. We propose the use of existing ecotoxicological community, food web, and ecosystem models to tackle these issues and discuss why new models are needed to predict chemical effects on biodiversity. Copyright © 2013 SETAC.

Injuries and Associated Risk Factors Among Adolescent Elite Orienteerers: A 26-Week Prospective Registration Study

PubMed Central

von Rosen, Philip; Heijne, Annette I.-L. M.; Frohm, Anna

2016-01-01

Context:  In orienteering, the number of injury-registration studies is limited. Most researchers have used a cross-sectional design during specific events and, therefore, have mainly identified acute injuries. Objective:  To determine the prevalence of injuries by registering acute and overuse injuries in adolescent elite orienteerers over 26 weeks and to study the variation of injury prevalence over the season and the potential risk factors. Design:  Cohort study. Setting:  Two high schools in Sweden with national orienteering teams. Patients or Other Participants:  All athletes (33 adolescent girls, 31 adolescent boys; age = 17 ± 1 years) from 2 high schools with orienteering teams. Main Outcome Measure(s):  We used a weekly Web-based questionnaire to identify the incidence and prevalence of injuries and training variables. Risk factors for injury were calculated using multiple linear regression techniques. Results:  The average weekly prevalence of overuse and acute injuries was 35.7% (95% confidence interval = 34.8%, 36.6%) and 1.7% (95% confidence interval = 1.3%, 2.1%), respectively; overuse injuries (78.0%, n = 85) accounted for the majority. The incidence of acute and overuse injuries was highest for the foot/lower leg (48.6%, n = 53), and 71.6% (n = 78) of all injuries affected the foot/lower leg and knee area. Time to the first reported injury was associated with training volume (β = 0.184, P = .001), competition time (β = −0.701, P = .009), running on asphalt roads (β = −0.348, P = .008), and running on forest surfaces and trails (β = −0.331, P = .007), with a model fit of r 2 = 0.50 (intercept = 2.196, P < .001). During the study, we observed a weekly increase (0.3%) in the prevalence of overuse injuries in the foot/lower leg (r 2 = 0.33, P = .001); the highest prevalence (26.9%) was at the beginning of the competitive season. Conclusions:  Overuse injuries, predominately in the foot/lower leg area, were more common than acute injuries in adolescent elite orienteerers. These injuries had the highest prevalence at the beginning of the competitive season; therefore, this period can be seen as a possible risk factor for sustaining overuse injuries in the foot/lower leg. PMID:27065190

Emergent behaviors of the Schrödinger-Lohe model on cooperative-competitive networks

NASA Astrophysics Data System (ADS)

Huh, Hyungjin; Ha, Seung-Yeal; Kim, Dohyun

2017-12-01

We present several sufficient frameworks leading to the emergent behaviors of the coupled Schrödinger-Lohe (S-L) model under the same one-body external potential on cooperative-competitive networks. The S-L model was first introduced as a possible phenomenological model exhibiting quantum synchronization and its emergent dynamics on all-to-all cooperative networks has been treated via two distinct approaches, Lyapunov functional approach and the finite-dimensional reduction based on pairwise correlations. In this paper, we further generalize the finite-dimensional dynamical systems approach for pairwise correlation functions on cooperative-competitive networks and provide several sufficient frameworks leading to the collective exponential synchronization. For small systems consisting of three and four quantum subsystem, we also show that the system for pairwise correlations can be reduced to the Lotka-Volterra model with cooperative and competitive interactions, in which lots of interesting dynamical patterns appear, e.g., existence of closed orbits and limit-cycles.

Risk management consideration in the bioeconomy

Treesearch

Camilla Abbati de Assis; Ronalds Gonzalez; Stephen Kelley; Hasan Jameel; Ted Bilek; Jesse Daystar; Robert Handfield; Jay Golden; Jeff Prestemon; Damien Singh

2017-01-01

In investing in a new venture, companies aim to increase their competitiveness and generate value in scenarios where volatile markets, geopolitical instabilities, and disruptive technologies create uncertainty and risk. The biobased industry poses additional challenges as it competes in a mature, highly efficient market, dominated by...

Two ways related to performance in elite sport: the path of self-confidence and competitive anxiety and the path of group cohesion and group goal-clarity.

PubMed

Kjørmo, Odd; Halvari, Hallgeir

2002-06-01

A model tested among 136 Norwegian Olympic-level athletes yielded two paths related to performance. The first path indicated that self-confidence, modeled as an antecedent of competitive anxiety, is negatively correlated with anxiety. Competitive anxiety in turn is negatively correlated with performance. The second path indicated that group cohesion is positively correlated with group goal-clarity, which in turn is positively correlated with performance. Competitive anxiety mediates the relation between self-confidence and performance, whereas group goal-clarity mediates the relation between group cohesion and performance. Results from multiple regression analyses supported the model in the total sample and among individual sport athletes organized in training groups (n = 100). Among team sport athletes (n = 36), personality and group measures are more strongly intercorrelated than among individual sport athletes, and the relation with performance is more complex for the former group. The interaction of self-confidence and competitive anxiety is related to performance among team sport athletes.

Generalized model of island biodiversity

NASA Astrophysics Data System (ADS)

Kessler, David A.; Shnerb, Nadav M.

2015-04-01

The dynamics of a local community of competing species with weak immigration from a static regional pool is studied. Implementing the generalized competitive Lotka-Volterra model with demographic noise, a rich dynamics with four qualitatively distinct phases is unfolded. When the overall interspecies competition is weak, the island species recapitulate the mainland species. For higher values of the competition parameter, the system still admits an equilibrium community, but now some of the mainland species are absent on the island. Further increase in competition leads to an intermittent "disordered" phase, where the dynamics is controlled by invadable combinations of species and the turnover rate is governed by the migration. Finally, the strong competition phase is glasslike, dominated by uninvadable states and noise-induced transitions. Our model contains, as a special case, the celebrated neutral island theories of Wilson-MacArthur and Hubbell. Moreover, we show that slight deviations from perfect neutrality may lead to each of the phases, as the Hubbell point appears to be quadracritical.

Generalized model of island biodiversity.

PubMed

Kessler, David A; Shnerb, Nadav M

2015-04-01

The dynamics of a local community of competing species with weak immigration from a static regional pool is studied. Implementing the generalized competitive Lotka-Volterra model with demographic noise, a rich dynamics with four qualitatively distinct phases is unfolded. When the overall interspecies competition is weak, the island species recapitulate the mainland species. For higher values of the competition parameter, the system still admits an equilibrium community, but now some of the mainland species are absent on the island. Further increase in competition leads to an intermittent "disordered" phase, where the dynamics is controlled by invadable combinations of species and the turnover rate is governed by the migration. Finally, the strong competition phase is glasslike, dominated by uninvadable states and noise-induced transitions. Our model contains, as a special case, the celebrated neutral island theories of Wilson-MacArthur and Hubbell. Moreover, we show that slight deviations from perfect neutrality may lead to each of the phases, as the Hubbell point appears to be quadracritical.

A hybrid of monopoly and perfect competition model for hi-tech products

NASA Astrophysics Data System (ADS)

Yang, P. C.; Wee, H. M.; Pai, S.; Yang, H. J.; Wee, P. K. P.

2010-11-01

For Hi-tech products, the demand rate, the component cost as well as the selling price usually decline significantly with time. In the case of perfect competition, shortages usually result in lost sales; while in a monopoly, shortages will be completely backordered. However, neither perfect competition nor monopoly exists. Therefore, there is a need to develop a replenishment model considering a hybrid of perfect competition and monopoly when the cost, price and demand are decreasing simultaneously. A numerical example and sensitivity analysis are carried out to illustrate this model. The results show that a higher decline-rate in the component cost leads to a smaller service level and a larger replenishment interval. When the component cost decline rate increases and the selling price decline rate decreases simultaneously, the replenishment interval decreases. In perfect competition it is better to have a high service level, while for the case with monopoly, keeping a low service level is better due to complete backordering.

Crude oil price dynamics: A study on effects of market expectation and strategic supply on price movements

NASA Astrophysics Data System (ADS)

Jin, Xin

Recent years have seen dramatic fluctuations in crude oil prices. This dissertation attempts to better understand price behavior. The first chapter studies the behavior of crude oil spot and futures prices. Oil prices, particularly spot and short-term futures prices, appear to have switched from I(0) to I(1) in early 2000s. To better understand this apparent change in persistence, a factor model of oil prices is proposed, where the prices are decomposed into long-term and short-term components. The change in the persistence behavior can be explained by changes in the relative volatility of the underlying components. Fitting the model to weekly data on WTI prices, the volatility of the persistent shocks increased substantially relative to other shocks. In addition, the risk premiums in futures prices have changed their signs and become more volatile. The estimated net marginal convenience yield using the model also shows changes in its behavior. These observations suggest that a dramatic fundamental change occurred in the period from 2002 to 2004 in the dynamics of the crude oil market. The second chapter explores the short-run price-inventory dynamics in the presence of different shocks. Classical competitive storage model states that inventory decision considers both current and future market condition, and thus interacts with spot and expected future spot prices. We study competitive storage holding in an equilibrium framework, focusing on the dynamic response of price and inventory to different shocks. We show that news shock generates response profile different from traditional contemporaneous shocks in price and inventory. The model is applied to world crude oil market, where the market expectation is estimated to experience a sharp change in early 2000s, together with a persisting constrained supply relative to demand. The expectation change has limited effect on crude oil spot price though. The world oil market structure has been studied extensively but no consensus has been reached on OPEC strategic behavior. In the third chapter, we are interested in the effects of supply-side market power on oil price dynamics in face of different demand shocks, and model the oil market as composed of a strategic dominant firm and several competitive fringe producers. In each period, the dominant firm makes decision while taking fringe's response into consideration. We consider two alternative pricing strategies for the dominant firm. Our results show that this dynamic strategic model improves the potential of dominant firm-competitive fringe model in fitting and explaining real world data. A regime switch after a permanent demand increase generates a time path for price that looks like the price movements in the recent years.

When Is It Too Early for Single Sport Specialization?

PubMed

Feeley, Brian T; Agel, Julie; LaPrade, Robert F

2016-01-01

Over the past 15 years, there has been an increase in youth sports participation with a concomitant increase in early year-round training in a single sport. Many factors contribute to the desire of parents and coaches to encourage early single sport specialization, including the desire to give the young athlete an edge in competition, pursuit of scholarships, and potential professional status, and the ability to label a young athlete as elite at an early age. Despite these perceived advantages, some data suggest that early sport specialization does not lead to a competitive advantage over athletes who participate in multiple sports. Although the data are limited, there is some evidence that early sport specialization may put the young athlete at risk for overuse injuries. The focus of this review is to highlight the evidence regarding early sport specialization and risk for injury; discuss the risk factors for overuse injury in high-risk sports including ice hockey, swimming, gymnastics, and baseball; and discuss future potential research that would help define the risk of injury for young athletes who participate in early sport specialization. © 2015 The Author(s).

The case for risk-based premiums in public health insurance.

PubMed

Zweifel, Peter; Breuer, Michael

2006-04-01

Uniform, risk-independent insurance premiums are accepted as part of 'managed competition' in health care. However, they are not compatible with optimality of health insurance contracts in the presence of both ex ante and ex post moral hazard. They have adverse effects on insurer behaviour even if risk adjustment is taken into account. Risk-based premiums combined with means-tested, tax-financed transfers are advocated as an alternative.

Risk management in medical product development process using traditional FMEA and fuzzy linguistic approach: a case study

NASA Astrophysics Data System (ADS)

Kirkire, Milind Shrikant; Rane, Santosh B.; Jadhav, Jagdish Rajaram

2015-12-01

Medical product development (MPD) process is highly multidisciplinary in nature, which increases the complexity and the associated risks. Managing the risks during MPD process is very crucial. The objective of this research is to explore risks during MPD in a dental product manufacturing company and propose a model for risk mitigation during MPD process to minimize failure events. A case study approach is employed. The existing MPD process is mapped with five phases of the customized phase gate process. The activities during each phase of development and risks associated with each activity are identified and categorized based on the source of occurrence. The risks are analyzed using traditional Failure mode and effect analysis (FMEA) and fuzzy FMEA. The results of two methods when compared show that fuzzy approach avoids the duplication of RPNs and helps more to convert cognition of experts into information to get values of risk factors. The critical, moderate, low level and negligible risks are identified based on criticality; risk treatments and mitigation model are proposed. During initial phases of MPD, the risks are less severe, but as the process progresses the severity of risks goes on increasing. The MPD process should be critically designed and simulated to minimize the number of risk events and their severity. To successfully develop the products/devices within the manufacturing companies, the process risk management is very essential. A systematic approach to manage risks during MPD process will lead to the development of medical products with expected quality and reliability. This is the first research of its kind having focus on MPD process risks and its management. The methodology adopted in this paper will help the developers, managers and researchers to have a competitive edge over the other companies by managing the risks during the development process.

The role of drought- and disturbance-mediated competition in shaping community responses to varied environments.

PubMed

Napier, Joseph D; Mordecai, Erin A; Heckman, Robert W

2016-06-01

By altering the strength of intra- and interspecific competition, droughts may reshape plant communities. Furthermore, species may respond differently to drought when other influences, such as herbivory, are considered. To explore this relationship, we conducted a greenhouse experiment measuring responses to inter- and intraspecific competition for two grasses, Schedonorus arundinaceus and Paspalum dilatatum, while varying water availability and simulating herbivory via clipping. We then parameterized population growth models to examine the long-term outcome of competition under these conditions. Under drought, S. arundinaceus was less water stressed than P. dilatatum, which exhibited severe water stress; clipping alleviated this stress, increasing the competitive ability of P. dilatatum relative to S. arundinaceus. Although P. dilatatum competed weakly under drought, clipping reduced water stress in P. dilatatum, thereby enhancing its ability to compete with S. arundinaceus under drought. Supporting these observations, population growth models predicted that P. dilatatum would exclude S. arundinaceus when clipped under drought, while S. arundinaceus would exclude P. dilatatum when unclipped under drought. When the modeled environment varied temporally, environmental variation promoted niche differences that, though insufficient to maintain stable coexistence, prevented unconditional competitive exclusion by promoting priority effects. Our results suggest that it is important to consider how species respond not just to stable, but also to variable, environments. When species differ in their responses to drought, competition, and simulated herbivory, stable environments may promote competitive exclusion, while fluctuating environments may promote coexistence. These interactions are critical to understanding how species will respond to global change.

Contrasting impacts of competition on ecological and social trait evolution in songbirds

PubMed Central

Tobias, Joseph A.; Burns, Kevin J.; Mason, Nicholas A.; Shultz, Allison J.; Morlon, Hélène

2018-01-01

Competition between closely related species has long been viewed as a powerful selective force that drives trait diversification, thereby generating phenotypic diversity over macroevolutionary timescales. However, although the impact of interspecific competition has been documented in a handful of iconic insular radiations, most previous studies have focused on traits involved in resource use, and few have examined the role of competition across large, continental radiations. Thus, the extent to which broad-scale patterns of phenotypic diversity are shaped by competition remain largely unclear, particularly for social traits. Here, we estimate the effect of competition between interacting lineages by applying new phylogenetic models that account for such interactions to an exceptionally complete dataset of resource-use traits and social signaling traits for the entire radiation of tanagers (Aves, Thraupidae), the largest family of songbirds. We find that interspecific competition strongly influences the evolution of traits involved in resource use, with a weaker effect on plumage signals, and very little effect on song. Our results provide compelling evidence that interspecific exploitative competition contributes to ecological trait diversification among coexisting species, even in a large continental radiation. In comparison, signal traits mediating mate choice and social competition seem to diversify under different evolutionary models, including rapid diversification in the allopatric stage of speciation. PMID:29385141

Contrasting impacts of competition on ecological and social trait evolution in songbirds.

PubMed

Drury, Jonathan P; Tobias, Joseph A; Burns, Kevin J; Mason, Nicholas A; Shultz, Allison J; Morlon, Hélène

2018-01-01

Competition between closely related species has long been viewed as a powerful selective force that drives trait diversification, thereby generating phenotypic diversity over macroevolutionary timescales. However, although the impact of interspecific competition has been documented in a handful of iconic insular radiations, most previous studies have focused on traits involved in resource use, and few have examined the role of competition across large, continental radiations. Thus, the extent to which broad-scale patterns of phenotypic diversity are shaped by competition remain largely unclear, particularly for social traits. Here, we estimate the effect of competition between interacting lineages by applying new phylogenetic models that account for such interactions to an exceptionally complete dataset of resource-use traits and social signaling traits for the entire radiation of tanagers (Aves, Thraupidae), the largest family of songbirds. We find that interspecific competition strongly influences the evolution of traits involved in resource use, with a weaker effect on plumage signals, and very little effect on song. Our results provide compelling evidence that interspecific exploitative competition contributes to ecological trait diversification among coexisting species, even in a large continental radiation. In comparison, signal traits mediating mate choice and social competition seem to diversify under different evolutionary models, including rapid diversification in the allopatric stage of speciation.

Influence of pre-pregnancy leisure time physical activity on gestational and postpartum weight gain and birth weight - a cohort study.

PubMed

Hegaard, Hanne Kristine; Rode, Line; Katballe, Malene Kjær; Langberg, Henning; Ottesen, Bent; Damm, Peter

2017-08-01

In order to examine the association between pre-pregnancy leisure time physical activities and gestational weight gain, postpartum weight gain and birth weight, we analysed prospectively collected data from 1827 women with singleton term pregnancies. Women were categorised in groups of sedentary women, light exercisers, moderate exercisers and competitive athletes. The results showed that sedentary women on average gained 14.1 kg during pregnancy, whereas light exercisers gained 13.7 kg, moderate exercisers gained 14.3 kg and competitive athletes 16.1 kg. Competitive athletes had an increased risk of having a gestational weight gain above Institute of Medicine (IOM) recommendations with an odds ratio of 2.60 (1.32-5.15) compared to light exercisers. However, birth weight and one year postpartum weight was similar for all four groups. Thus, although competitive athletes gain more weight than recommended during pregnancy, this may not affect birth weight or postpartum weight. Impact statement What is already known on this subjectPrevious studies have found that increased pre-pregnancy physical activity is associated with lower gestational weight gain during the last trimester, but showed no association between the pre-pregnancy level of physical activity and mean birth weight. What the results of this study addWe found that women classified as competitive exercisers had a 2.6-fold increased risk of gaining more weight than recommended compared to light exercisers. Nearly 6 out of 10 women among the competitive exercisers gained more weight than recommended by IOM. Surprisingly, this did not appear to increase birth weight or post-partum weight gain, but other adverse effects cannot be excluded. What the implications are of these findings for clinical practice and/or further researchIn the clinical practice it may be relevant to focus on and advise pre-pregnancy competitive exercisers in order to prevent excessive gestational weight gain.

[Cardiovascular clearance for competitive sport in aging people].

PubMed

Carré, François

2013-06-01

The regular sport practice slows the physiological deleterious effects of aging. However, during intense exercise, the hazard of acute cardiovascular event is significantly increased. Whatever their cardiovascular risk factors are, aging people are more prone to coronary acute event during intense exertion than a young one. Cardiovascular exam, with resting ECG and maximal exercise test, is needed to give clearance for competitive sport in aging people (>65 y.o.). The limited value to evaluate the individual risk of acute cardiac event during intense exercise must be clearly explained to Master athletes. They must be aware to the necessity to consult their physician in case of abnormal symptom during exercise. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

The importance of motivation, weapons, and foul odors in driving encounter competition in carnivores.

PubMed

Allen, Maximilian L; Wilmers, Christopher C; Elbroch, L Mark; Golla, Julie M; Wittmer, Heiko U

2016-08-01

Encounter competition is interference competition in which animals directly contend for resources. Ecological theory predicts the trait that determines the resource holding potential (RHP), and hence the winner of encounter competition, is most often body size or mass. The difficulties of observing encounter competition in complex organisms in natural environments, however, has limited opportunities to test this theory across diverse species. We studied the outcome of encounter competition contests among mesocarnivores at deer carcasses in California to determine the most important variables for winning these contests. We found some support for current theory in that body mass is important in determining the winner of encounter competition, but we found that other factors including hunger and species-specific traits were also important. In particular, our top models were "strength and hunger" and "size and hunger," with models emphasizing the complexity of variables influencing outcomes of encounter competition. In addition, our wins above predicted (WAP) statistic suggests that an important aspect that determines the winner of encounter competition is species-specific advantages that increase their RHP, as bobcats (Lynx rufus) and spotted skunks (Spilogale gracilis) won more often than predicted based on mass. In complex organisms, such as mesocarnivores, species-specific adaptations, including strategic behaviors, aggressiveness, and weapons, contribute to competitive advantages and may allow certain species to take control or defend resources better than others. Our results help explain how interspecific competition shapes the occurrence patterns of species in ecological communities. © 2016 by the Ecological Society of America.

Validation of a Seven-Factor Structure for the Motives for Playing Drinking Games Measure.

PubMed

Zamboanga, Byron L; Audley, Shannon; Olthuis, Janine V; Blumenthal, Heidemarie; Tomaso, Cara C; Bui, Ngoc; Borsari, Brian

2017-04-01

Playing drinking games can be characterized as a high-risk drinking activity because games are typically designed to promote heavy alcohol consumption. While research suggests that young adults are motivated to play drinking games for a variety of reasons (e.g., for thrills/fun, for the competition), the Motives for Playing Drinking Games measure has received limited empirical attention. We examined the psychometric properties of this measure with a confirmation sample of young adults recruited from Amazon's MTurk ( N = 1,809, ages 18-25 years, 47% men; 41% not currently enrolled in college) and a validation sample of college students ( N = 671; ages 18-23 years; 26% men). Contrary to the 8-factor model obtained by Johnson and Sheets in a study published in 2004, examination of the factor structure with our confirmation sample yielded a revised 7-factor model that was invariant across race/ethnicity and college student status. This model was also validated with the college student sample. In the confirmation sample, enhancement/thrills and sexual pursuit motives for playing drinking games were positively associated with gaming frequency/consumption and negative gaming consequences. Furthermore, conformity motives for playing drinking games were positively associated with negative gaming consequences, while competition motives were positively associated with gaming frequency. These findings have significant implications for research and prevention/intervention efforts.

Predicting the sensitivity of populations from individual exposure to chemicals: the role of ecological interactions.

PubMed

Gabsi, Faten; Schäffer, Andreas; Preuss, Thomas G

2014-07-01

Population responses to chemical stress exposure are influenced by nonchemical, environmental processes such as species interactions. A realistic quantification of chemical toxicity to populations calls for the use of methodologies that integrate these multiple stress effects. The authors used an individual-based model for Daphnia magna as a virtual laboratory to determine the influence of ecological interactions on population sensitivity to chemicals with different modes of action on individuals. In the model, hypothetical chemical toxicity targeted different vital individual-level processes: reproduction, survival, feeding rate, or somatic growth rate. As for species interactions, predatory and competition effects on daphnid populations were implemented following a worst-case approach. The population abundance was simulated at different food levels and exposure scenarios, assuming exposure to chemical stress solely or in combination with either competition or predation. The chemical always targeted one vital endpoint. Equal toxicity-inhibition levels differently affected the population abundance with and without species interactions. In addition, population responses to chemicals were highly sensitive to the environmental stressor (predator or competitor) and to the food level. Results show that population resilience cannot be attributed to chemical stress only. Accounting for the relevant ecological interactions would reduce uncertainties when extrapolating effects of chemicals from individuals to the population level. Validated population models should be used for a more realistic risk assessment of chemicals. © 2014 SETAC.

Does long-distance air travel associated with the Sevens World Series increase players' risk of injury?

PubMed

Fuller, Colin W; Taylor, Aileen E; Raftery, Martin

2015-04-01

To assess whether players who cross ≥6 time zones and/or undertake ≥10 h air travel prior to competition experience a higher risk of injury during the Sevens World Series than players not required to undertake this level of travel. Five-year, prospective, cohort study. All players from nine core teams competing in the Sevens World Series from 2008/2009 to 2013/2014. A total of 436 match injuries and 3363 player-match-hours of exposure were recorded in the study, which corresponds to an overall incidence of 129.6 injuries/1000 player-match-hours, irrespective of the nature of pretournament travel. The incidence of injury for those players crossing ≥6 time zones and undertaking ≥10 h air travel prior to competition (99.3 injuries/1000 player-match-hours) was significantly lower than that of players undertaking ≥10 h air travel but crossing ≤2 time zones prior to competition (148.8 injuries/1000 player-match-hours; p=0.003) and of those undertaking ≤3 h air travel and crossing ≤2 time zones prior to competition (146.4 injuries/1000 player-match-hours; p=0.004). There was no significant difference in the incidence of injury for players crossing ≤2 time zones in the week prior to competition, irrespective of whether the length of air travel was ≤3 h or ≥10 h (p=0.904). Precompetition air travel had no significant effect (p=0.879) on the performance of teams in terms of their final Tournament ranking positions. There was no evidence to suggest that players were exposed to a greater risk of injury following extensive air travel and crossing multiple time zones prior to Tournaments in the Sevens World Series. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Factors related to rural young adolescents' participation in outdoor, noncompetitive physical activity.

PubMed

Christiana, Richard W; Davis, Marsha; Wilson, Mark G; McCarty, Frances A; Green, Gary T

2014-12-01

Young adolescents who have little interest in participating in competitive team sports are at an increased risk for physical inactivity. Noncompetitive outdoor physical activity can provide young adolescents with increased opportunities to participate in physical activities that appeal to them and have positive health effects. The purpose of this study was to examine factors related to rural young adolescents' participation in noncompetitive outdoor physical activity to inform intervention design. Young adolescents aged 10 to 14 years old (N = 1,032) from 1 rural county completed a self-administered questionnaire assessing constructs from self-determination theory (SDT) and the theory of planned behavior (TPB) related to noncompetitive outdoor physical activity. Structural equation modeling was used to examine an integrated conceptual model of hypothesized relationships among constructs. The hypothesized conceptual model provided a good fit to the data with greater perceptions of autonomy support and self-determined motivation having statistically significant positive indirect effects on participation in noncompetitive outdoor physical activity mediated by the constructs of the TPB. All direct paths in the model were statistically significant; however, the direct effect of attitudes on intention was weak (.08) and self-determined motivation had no indirect effect on intention through attitudes (.03). Constructs of SDT and TPB should be accounted for by interventions targeting noncompetitive outdoor physical activity among young adolescents. More research is needed to determine young adolescents' preferences for noncompetitive and competitive physical activity and the potential influence that noncompetitive outdoor physical activity may have on total daily physical activity.

Multi-factor energy price models and exotic derivatives pricing

NASA Astrophysics Data System (ADS)

Hikspoors, Samuel

The high pace at which many of the world's energy markets have gradually been opened to competition have generated a significant amount of new financial activity. Both academicians and practitioners alike recently started to develop the tools of energy derivatives pricing/hedging as a quantitative topic of its own. The energy contract structures as well as their underlying asset properties set the energy risk management industry apart from its more standard equity and fixed income counterparts. This thesis naturally contributes to these broad market developments in participating to the advances of the mathematical tools aiming at a better theory of energy contingent claim pricing/hedging. We propose many realistic two-factor and three-factor models for spot and forward price processes that generalize some well known and standard modeling assumptions. We develop the associated pricing methodologies and propose stable calibration algorithms that motivate the application of the relevant modeling schemes.

Customer social network affects marketing strategy: A simulation analysis based on competitive diffusion model

NASA Astrophysics Data System (ADS)

Hou, Rui; Wu, Jiawen; Du, Helen S.

2017-03-01

To explain the competition phenomenon and results between QQ and MSN (China) in the Chinese instant messaging software market, this paper developed a new population competition model based on customer social network. The simulation results show that the firm whose product with greater network externality effect will gain more market share than its rival when the same marketing strategy is used. The firm with the advantage of time, derived from the initial scale effect will become more competitive than its rival when facing a group of common penguin customers within a social network, verifying the winner-take-all phenomenon in this case.

Resource competition induces heterogeneity and can increase cohort survivorship: selection-event duration matters.

PubMed

Gosselin, Jennifer L; Anderson, James J

2013-12-01

Determining when resource competition increases survivorship can reveal processes underlying population dynamics and reinforce the importance of heterogeneity among individuals in conservation. We ran an experiment mimicking the effects of competition in a growing season on survivorship during a selection event (e.g., overwinter starvation, drought). Using a model fish species (Poecilia reticulata), we studied how food availability and competition affect mass in a treatment stage, and subsequently survivorship in a challenge stage of increased temperature and starvation. The post-treatment mean mass was strongly related to the mean time to mortality and mass at mortality at all levels of competition. However, competition increased variance in mass and extended the right tail of the survivorship curve, resulting in a greater number of individuals alive beyond a critical temporal threshold ([Formula: see text]) than without competition. To realize the benefits from previously experienced competition, the duration of the challenge ([Formula: see text]) following the competition must exceed the critical threshold [Formula: see text] (i.e., competition increases survivorship when [Formula: see text]). Furthermore, this benefit was equivalent to increasing food availability by 20 % in a group without competition in our experiment. The relationship of [Formula: see text] to treatment and challenge conditions was modeled by characterizing mortality through mass loss in terms of the stochastic rate of loss of vitality (individual's survival capacity). In essence, when the duration of a selection event exceeds [Formula: see text], competition-induced heterogeneity buffers against mortality through overcompensation processes among individuals of a cohort. Overall, our study demonstrates an approach to quantify how early life stage heterogeneity affects survivorship.

Differential transcriptional regulation by alternatively designed mechanisms: A mathematical modeling approach.

PubMed

Yildirim, Necmettin; Aktas, Mehmet Emin; Ozcan, Seyma Nur; Akbas, Esra; Ay, Ahmet

2017-01-01

Cells maintain cellular homeostasis employing different regulatory mechanisms to respond external stimuli. We study two groups of signal-dependent transcriptional regulatory mechanisms. In the first group, we assume that repressor and activator proteins compete for binding to the same regulatory site on DNA (competitive mechanisms). In the second group, they can bind to different regulatory regions in a noncompetitive fashion (noncompetitive mechanisms). For both competitive and noncompetitive mechanisms, we studied the gene expression dynamics by increasing the repressor or decreasing the activator abundance (inhibition mechanisms), or by decreasing the repressor or increasing the activator abundance (activation mechanisms). We employed delay differential equation models. Our simulation results show that the competitive and noncompetitive inhibition mechanisms exhibit comparable repression effectiveness. However, response time is fastest in the noncompetitive inhibition mechanism due to increased repressor abundance, and slowest in the competitive inhibition mechanism by increased repressor level. The competitive and noncompetitive inhibition mechanisms through decreased activator abundance show comparable and moderate response times, while the competitive and noncompetitive activation mechanisms by increased activator protein level display more effective and faster response. Our study exemplifies the importance of mathematical modeling and computer simulation in the analysis of gene expression dynamics.

Resource and competitive dynamics shape the benefits of public goods cooperation in a plant pathogen

PubMed Central

Platt, Thomas G.; Fuqua, Clay; Bever, James D.

2012-01-01

Cooperative benefits depend on a variety of ecological factors. Many cooperative bacteria increase the population size of their groups by making a public good available. Increased local population size can alleviate the constraints of kin competition on the evolution of cooperation by enhancing the between-group fitness of cooperators. The cooperative pathogenesis of Agrobacterium tumefaciens causes infected plants to exude opines—resources that provide a nearly exclusive source of nutrient for the pathogen. We experimentally demonstrate that opines provide cooperative A. tumefaciens cells a within-group fitness advantage over saprophytic agrobacteria. Our results are congruent with a resource-consumer competition model, which predicts that cooperative, virulent agrobacteria are at a competitive disadvantage when opines are unavailable, but have an advantage when opines are available at sufficient levels. This model also predicts that freeloading agrobacteria that catabolize opines but cannot infect plants competitively displace the cooperative pathogen from all environments. However, we show that these cooperative public goods also promote increased local population size. A model built from the Price Equation shows that this effect on group size can contribute to the persistence of cooperative pathogenesis despite inherent kin competition for the benefits of pathogenesis. PMID:22671559

Community trait overdispersion due to trophic interactions: concerns for assembly process inference

PubMed Central

Petchey, Owen L.

2016-01-01

The expected link between competitive exclusion and community trait overdispersion has been used to infer competition in local communities, and trait clustering has been interpreted as habitat filtering. Such community assembly process inference has received criticism for ignoring trophic interactions, as competition and trophic interactions might create similar trait patterns. While other theoretical studies have generally demonstrated the importance of predation for coexistence, ours provides the first quantitative demonstration of such effects on assembly process inference, using a trait-based ecological model to simulate the assembly of a competitive primary consumer community with and without the influence of trophic interactions. We quantified and contrasted trait dispersion/clustering of the competitive communities with the absence and presence of secondary consumers. Trophic interactions most often decreased trait clustering (i.e. increased dispersion) in the competitive communities due to evenly distributed invasions of secondary consumers and subsequent competitor extinctions over trait space. Furthermore, effects of trophic interactions were somewhat dependent on model parameters and clustering metric. These effects create considerable problems for process inference from trait distributions; one potential solution is to use more process-based and inclusive models in inference. PMID:27733548

A specter of coexistence: Is centrifugal community organization haunted by the ghost of competition?

USGS Publications Warehouse

Wasserberg, Gideon; Kotler, B.P.; Morris, D.W.; Abramsky, Z.

2006-01-01

In a centrifugally organized community species prefer the same habitat (called "core") but differ in their secondary habitat preferences. The first model of centrifugal community organization (CCO) predicted that optimally foraging, symmetrically competing species would share use of the core habitat at all density combinations. But one might also assume that the competition in the core habitat is asymmetrical, that is, that one of the species (the dominant) has a behavioral advantage therein. In this study, we asked how should habitat use evolve in a centrifugally organized community if its species compete asymmetrically in the core habitat? To address this question we developed an "isoleg model". The model predicts that in a centrifugally organized community, asymmetric competition promotes the use of the core habitat exclusively by the dominant species at most points in the state space. The separation of the core habitat use by the species ("the ghost of competition past") may be either complete or partial ("partial ghost"), and behavior at the stable competitive equilibrium between the species could determine whether coexistence should occur at the "complete-" or the "partial ghost" regions. This version of CCO should be a common feature of competitive systems.

The effects of hospital competition on inpatient quality of care.

PubMed

Mutter, Ryan L; Wong, Herbert S; Goldfarb, Marsha G

2008-01-01

Existing empirical studies have produced inconclusive, and sometimes contradictory, findings on the effects of hospital competition on inpatient quality of care. These inconsistencies may be due to the use of different methodologies, hospital competition measures, and hospital quality measures. This paper applies the Quality Indicator software from the Agency for Healthcare Research and Quality to the 1997 Healthcare Cost and Utilization Project State Inpatient Databases to create three versions (i.e., observed, risk-adjusted, and "smoothed") of 38 distinct measures of inpatient quality. The relationship between 12 different hospital competition measures and these quality measures are assessed, using ordinary least squares, two-step efficient generalized method of moments, and negative binomial regression techniques. We find that across estimation strategies, hospital competition has an impact on a number of hospital quality measures. However, the effect is not unidirectional: some indicators show improvements in hospital quality with greater levels of competition, some show decreases in hospital quality, and others are unaffected. We provide hypotheses based on emerging areas of research that could explain these findings, but inconsistencies remain.

Personal experiences of people with serious mental illness when seeking, obtaining and maintaining competitive employment in Queensland, Australia.

PubMed

Gladman, Beverley; Waghorn, Geoff

2016-02-15

High non-participation in the labour force and unemployment remain challenging for adults with serious mental illness. This study examined the personal experiences of people with serious mental illness when seeking, obtaining and maintaining competitive employment. The aim was to increase understanding of personal experiences of employment and how these experiences can be used to inform the assistance provided in support of clients' competitive employment goals. Qualitative data from a two-year period were thematically analysed from one participating site in a multi-site trial of employment services integrated with public funded community mental health treatment and care. Both positive and negative themes arose. Positive themes included: Aspirations for a better life, receiving feedback on good job performance, employment displacing preoccupation with illness, and employment improving self-esteem and reducing financial stress. Negative themes included stigma experiences, stress, and health difficulties. Both positive and negative experiences did not depend on type of employment service assistance nor key client characteristics such as age, sex, and diagnostic category. Despite its many benefits, employment can also increase the risk of negative personal experiences. These findings suggest that employment service providers could do more to assist people who commence employment, to reduce the risk of negative personal experiences and to enhance the benefits of competitive employment.

CO2 enrichment and carbon partitioning to phenolics: do plant responses accord better with the protein competition or the growth-differentiation balance models?

Treesearch

W.J. Mattson; R. Julkunen-Tiitto; D.A. Herms

2005-01-01

Rising levels of atmospheric CO2 can alter plant growth and partitioning to secondary metabolites. The protein competition model (PCM) and the extended growth/differentiation balance model (GDBe) are similar but alternative models that address ontogenetic and environmental effects on whole-plant carbon partitioning to the...

An agent-based model for emotion contagion and competition in online social media

NASA Astrophysics Data System (ADS)

Fan, Rui; Xu, Ke; Zhao, Jichang

2018-04-01

Recent studies suggest that human emotions diffuse in not only real-world communities but also online social media. However, a comprehensive model that considers up-to-date findings and multiple online social media mechanisms is still missing. To bridge this vital gap, an agent-based model, which concurrently considers emotion influence and tie strength preferences, is presented to simulate the emotion contagion and competition. Our model well reproduces patterns observed in the empirical data, like anger's preference on weak ties, anger-dominated users' high vitalities and angry tweets' short retweet intervals, and anger's competitiveness in negative events. The comparison with a previously presented baseline model further demonstrates its effectiveness in modeling online emotion contagion. It is also surprisingly revealed by our model that as the ratio of anger approaches joy with a gap less than 12%, anger will eventually dominate the online social media and arrives the collective outrage in the cyber space. The critical gap disclosed here can be indeed warning signals at early stages for outrage control. Our model would shed lights on the study of multiple issues regarding emotion contagion and competition in terms of computer simulations.

77 FR 38804 - Wireline Competition Bureau Seeks Comment on Model Design and Data Inputs for Phase II of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-29

...In this document, the Wireline Competition Bureau (the Bureau) seeks comment on a number of threshold decisions regarding the design of and data inputs to the forward looking cost model, and on other assumptions in the cost models currently in the record.

Developing Staffing Models to Support Population Health Management And Quality Oucomes in Ambulatory Care Settings.

PubMed

Haas, Sheila A; Vlasses, Frances; Havey, Julia

2016-01-01

There are multiple demands and challenges inherent in establishing staffing models in ambulatory heath care settings today. If health care administrators establish a supportive physical and interpersonal health care environment, and develop high-performing interprofessional teams and staffing models and electronic documentation systems that track performance, patients will have more opportunities to receive safe, high-quality evidence-based care that encourages patient participation in decision making, as well as provision of their care. The health care organization must be aligned and responsive to the community within which it resides, fully invested in population health management, and continuously scanning the environment for competitive, regulatory, and external environmental risks. All of these challenges require highly competent providers willing to change attitudes and culture such as movement toward collaborative practice among the interprofessional team including the patient.

Competitive employment training for mentally retarded adults: the supported work model.

PubMed

Krauss, M W; MacEachron, A E

1982-05-01

The supported work model designed to train mentally retarded persons for competitive employment, was initiated as a pilot program in 1979. The placement rate was 50 percent. In order to investigate the predictors of placement, we conducted an empirical analysis using the theory of work adjustment perspective. Results indicated that the participant's work behavior and job skills, ability to meet the requirements of the jobs, and employment reinforcements were predictors of competitive placement.

Clean Energy Manufacturing Initiative Solid-State Lighting

ScienceCinema

Thomas, Sunil; Edmond, John; Krames, Michael; Rama

2018-05-30

The importance of U.S. manufacturing for clean energy technologies, such as solid-state lighting (SSL), is paramount to increasing competitiveness in a global marketplace. SSLs are poised to drive the lighting market, worldwide. In order to continue that competitiveness and support further innovation, the time to invest in U.S. manufacturing of clean energy technologies is now. Across the country, companies developing innovative clean energy technologies find competitive advantages to manufacturing in the U.S. The Department of Energy's Building Technology Office SSL Manufacturing Roadmap is just one example of how we support manufacturing through convening industry perspectives on opportunities to significantly reduce risk, improve quality, increase yields, and lower costs.

Bifurcation structure of positive stationary solutions for a Lotka-Volterra competition model with diffusion I

NASA Astrophysics Data System (ADS)

Kan-On, Yukio

2007-04-01

This paper is concerned with the bifurcation structure of positive stationary solutions for a generalized Lotka-Volterra competition model with diffusion. To establish the structure, the bifurcation theory and the interval arithmetic are employed.

Models of Experimentally Derived Competitive Effects Predict Biogeographical Differences in the Abundance of Invasive and Native Plant Species

PubMed Central

Xiao, Sa; Ni, Guangyan; Callaway, Ragan M.

2013-01-01

Mono-dominance by invasive species provides opportunities to explore determinants of plant distributions and abundance; however, linking mechanistic results from small scale experiments to patterns in nature is difficult. We used experimentally derived competitive effects of an invader in North America, Acroptilon repens, on species with which it co-occurs in its native range of Uzbekistan and on species with which it occurs in its non-native ranges in North America, in individual-based models. We found that competitive effects yielded relative abundances of Acroptilon and other species in models that were qualitatively similar to those observed in the field in the two ranges. In its non-native range, Acroptilon can occur in nearly pure monocultures at local scales, whereas such nearly pure stands of Acroptilon appear to be much less common in its native range. Experimentally derived competitive effects of Acroptilon on other species predicted Acroptilon to be 4–9 times more proportionally abundant than natives in the North American models, but proportionally equal to or less than the abundance of natives in the Eurasian models. Our results suggest a novel way to integrate complex combinations of interactions simultaneously, and that biogeographical differences in the competitive effects of an invader correspond well with biogeographical differences in abundance and impact. PMID:24265701

Competition in the health system: good news and bad news.

PubMed

Miller, R H

1996-01-01

Competition among health plans, hospitals, and physicians has taken place in fifteen health care markets primarily on the basis of price and secondarily on network breadth and style of care. In most markets, competition resulted in lower (or slowly growing) premium prices. Within a type of plan product, competition was leading to similar prices and networks and was reducing product differentiation among health plans. Competition was not taking place on the basis of measured and reported quality of care, which limited the capacity of employers and enrollees to make informed health plan choices. As a result, there was a substantial gap between competition as envisioned by the architects of the managed competition model and competition as it is evolving today.

EPA Recognized for Research on Reducing Risks to Drinking ...

EPA Pesticide Factsheets

Technical Brief Threat Ensemble Vulnerability Assessment (TEVA) among finalists for Edelman Award On February 7, 2008, the Institute for Operations Research and the Management Sciences (INFORMS ® of Hanover, MD) announced that a TEVA Research project is one of six finalists vying for this year’s prestigious Franz Edelman Award. The project is called “Reducing Security Risks in American Drinking Water Systems.” Edelman Award Information This is the thirty-seventh year of the Edelman competition. Every year, the competition recognizes outstanding operations research-based projects that transform companies, entire industries, and people’s lives. Operations research uses advanced analytical methods to make optimal decisions in order to solve complex problems. The winner of the award will be announced in mid-April 2008. Past Edelman Award finalists include Travelocity; IBM; Merrill Lynch; the Memorial Sloan-Kettering Cancer Center; and Georgia Tech. The winning team for 2007 reduced both patient suffering and health care costs from the treatment of prostate and breast cancer. The Edelman competition attests to the contributions of operations research in the profit and nonprofit sectors. It is estimated that the cumulative dollar benefits from Edelman finalist projects between 1984 and 2006 reached the $100 billion mark. TEVA Research Program The TEVA research program has focused on reducing the security risks to drinking water systems. Ad

Modelling of optimal training load patterns during the 11 weeks preceding major competition in elite swimmers.

PubMed

Hellard, Philippe; Scordia, Charlotte; Avalos, Marta; Mujika, Inigo; Pyne, David B

2017-10-01

Periodization of swim training in the final training phases prior to competition and its effect on performance have been poorly described. We modeled the relationships between the final 11 weeks of training and competition performance in 138 elite sprint, middle-distance, and long-distance swimmers over 20 competitive seasons. Total training load (TTL), strength training (ST), and low- to medium-intensity and high-intensity training variables were monitored. Training loads were scaled as a percentage of the maximal volume measured at each intensity level. Four training periods (meso-cycles) were defined: the taper (weeks 1 to 2 before competition), short-term (weeks 3 to 5), medium-term (weeks 6 to 8), and long-term (weeks 9 to 11). Mixed-effects models were used to analyze the association between training loads in each training meso-cycle and end-of-season major competition performance. For sprinters, a 10% increase between ∼20% and 70% of the TTL in medium- and long-term meso-cycles was associated with 0.07 s and 0.20 s faster performance in the 50 m and 100 m events, respectively (p < 0.01). For middle-distance swimmers, a higher TTL in short-, medium-, and long-term training yielded faster competition performance (e.g., a 10% increase in TTL was associated with improvements of 0.1-1.0 s in 200 m events and 0.3-1.6 s in 400 m freestyle, p < 0.01). For sprinters, a 60%-70% maximal ST load 6-8 weeks before competition induced the largest positive effects on performance (p < 0.01). An increase in TTL during the medium- and long-term preparation (6-11 weeks to competition) was associated with improved performance. Periodization plans should be adapted to the specialty of swimmers.

Elucidating the interaction between light competition and herbivore feeding patterns using functional–structural plant modelling

PubMed Central

de Vries, Jorad; Poelman, Erik H; Anten, Niels; Evers, Jochem B

2018-01-01

Abstract Background and Aims Plants usually compete with neighbouring plants for resources such as light as well as defend themselves against herbivorous insects. This requires investment of limiting resources, resulting in optimal resource distribution patterns and trade-offs between growth- and defence-related traits. A plant’s competitive success is determined by the spatial distribution of its resources in the canopy. The spatial distribution of herbivory in the canopy in turn differs between herbivore species as the level of herbivore specialization determines their response to the distribution of resources and defences in the canopy. Here, we investigated to what extent competition for light affects plant susceptibility to herbivores with different feeding preferences. Methods To quantify interactions between herbivory and competition, we developed and evaluated a 3-D spatially explicit functional–structural plant model for Brassica nigra that mechanistically simulates competition in a dynamic light environment, and also explicitly models leaf area removal by herbivores with different feeding preferences. With this novel approach, we can quantitatively explore the extent to which herbivore feeding location and light competition interact in their effect on plant performance. Key Results Our results indicate that there is indeed a strong interaction between levels of plant–plant competition and herbivore feeding preference. When plants did not compete, herbivory had relatively small effects irrespective of feeding preference. Conversely, when plants competed, herbivores with a preference for young leaves had a strong negative effect on the competitiveness and subsequent performance of the plant, whereas herbivores with a preference for old leaves did not. Conclusions Our study predicts how plant susceptibility to herbivory depends on the composition of the herbivore community and the level of plant competition, and highlights the importance of considering the full range of dynamics in plant–plant–herbivore interactions. PMID:29373660

Steps to reduce favorable risk selection in medicare advantage largely succeeded, boding well for health insurance exchanges

PubMed Central

Newhouse, Joseph P.; Price, Mary; Huang, Jie; McWilliams, J. Michael; Hsu, John

2012-01-01

Managing competition among health plans that attract different risks has been a challenging policy problem. Within Medicare, the Medicare Advantage (MA) program historically attracted better risks than did Traditional Medicare (TM). This favorable selection resulted in Medicare’s paying more for persons enrolled in MA than if they had been enrolled in TM. We studied whether policies Medicare implemented in the past decade to reduce favorable selection in the MA program succeeded, in particular improved matching of reimbursement with a beneficiary’s expected cost and restricting when beneficiaries could switch from MA to TM. We found they did. Differences in predicted spending between those switching from TM to MA relative to those who remained in TM markedly narrowed, as did adjusted mortality rates. Because insurance exchanges will employ similar policies to combat selection, our results give reason for optimism about managing competition among health plans. PMID:23213145

Competition for light and nutrients in layered communities of aquatic plants.

PubMed

van Gerven, Luuk P A; de Klein, Jeroen J M; Gerla, Daan J; Kooi, Bob W; Kuiper, Jan J; Mooij, Wolf M

2015-07-01

Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at high supply of light and nutrients, floating plants always dominate due to their primacy for light, even when submerged plants have lower minimal resource requirements. The model also shows that floating-plant dominance cannot be an alternative stable state in light-limited environments but only in nutrient-limited environments, depending on the plants' resource consumption traits. Compared to unlayered communities, the asymmetry in competition for light-coincident with symmetry in competition for nutrients-leads to fundamentally different results: competition outcomes can no longer be predicted from species traits such as minimal resource requirements ([Formula: see text] rule) and resource consumption. Also, the same two species can, depending on the environment, coexist or be alternative stable states. When applied to two common plant species in temperate regions, both the model and field data suggest that floating-plant dominance is unlikely to be an alternative stable state.

Environmental structure and competitive scoring advantages in team competitions.

PubMed

Merritt, Sears; Clauset, Aaron

2013-10-29

In most professional sports, playing field structure is kept neutral so that scoring imbalances may be attributed to differences in team skill. It thus remains unknown what impact environmental heterogeneities can have on scoring dynamics or competitive advantages. Applying a novel generative model of scoring dynamics to roughly 10 million team competitions drawn from an online game, we quantify the relationship between the structure within a competition and its scoring dynamics, while controlling the impact of chance. Despite wide structural variations, we observe a common three-phase pattern in the tempo of events. Tempo and balance are highly predictable from a competition's structural features alone and teams exploit environmental heterogeneities for sustained competitive advantage. Surprisingly, the most balanced competitions are associated with specific environmental heterogeneities, not from equally skilled teams. These results shed new light on the design principles of balanced competition, and illustrate the potential of online game data for investigating social dynamics and competition.

Environmental structure and competitive scoring advantages in team competitions

NASA Astrophysics Data System (ADS)

Merritt, Sears; Clauset, Aaron

2013-10-01

In most professional sports, playing field structure is kept neutral so that scoring imbalances may be attributed to differences in team skill. It thus remains unknown what impact environmental heterogeneities can have on scoring dynamics or competitive advantages. Applying a novel generative model of scoring dynamics to roughly 10 million team competitions drawn from an online game, we quantify the relationship between the structure within a competition and its scoring dynamics, while controlling the impact of chance. Despite wide structural variations, we observe a common three-phase pattern in the tempo of events. Tempo and balance are highly predictable from a competition's structural features alone and teams exploit environmental heterogeneities for sustained competitive advantage. Surprisingly, the most balanced competitions are associated with specific environmental heterogeneities, not from equally skilled teams. These results shed new light on the design principles of balanced competition, and illustrate the potential of online game data for investigating social dynamics and competition.

Decentralized supply chain network design: monopoly, duopoly and oligopoly competitions under uncertainty

NASA Astrophysics Data System (ADS)

Seyedhosseini, Seyed Mohammad; Fahimi, Kaveh; Makui, Ahmad

2017-12-01

This paper presents the competitive supply chain network design problem in which n decentralized supply chains simultaneously enter the market with no existing rival chain, shape their networks and set wholesale and retail prices in competitive mode. The customer demand is elastic and price dependent, customer utility function is based on the Hoteling model and the chains produce identical or highly substitutable products. We construct a solution algorithm based on bi-level programming and possibility theory. In the proposed bi-level model, the inner part sets the prices based on simultaneous extra- and Stackleberg intra- chains competitions, and the outer part shapes the networks in cooperative competitions. Finally, we use a real-word study to discuss the effect of the different structures of the competitors on the equilibrium solution. Moreover, sensitivity analyses are conducted and managerial insights are offered.

Impact of price deregulation policy on the affordability of essential medicines for women's health: a panel data analysis.

PubMed

Liu, Junjie; Wang, Liming; Liu, Chenxi; Zhang, Xinping

2017-12-01

A new policy which required deregulation on prices of off-patent medicines for women's health during procurement was introduced in China in September 2015. The current study examines this policy's impact on the affordability of essential medicines for women's health. Based on product-level panel data, a fixed effect regression model is employed by using procurement records from Hubei Centralist Tender for Drug Purchase platform. In the model, Affordability was measured with prices. The Competition consists of two parts: generic competition and therapeutic class competition which are measured with generic competitors and therapeutic substitutes. Instrument variable is used to deal with endogeneity. The policy helped control prices of essential medicines for women's health. Generic competition helped control prices, however, therapeutic class competition caused higher prices. The new policy helped enhance the affordability of essential medicines for women's health as expected, which provides empirical evidence on price deregulation. Besides, generic competition is important in price control despite strict regulatory system in China.

Occupational sedentariness and breast cancer risk.

PubMed

Johnsson, Anna; Broberg, Per; Johnsson, Anders; Tornberg, Åsa B; Olsson, Håkan

2017-01-01

Epidemiological studies have indicated that physical activity reduces the risk of developing breast cancer. More recently, sedentary behavior has been suggested as a risk factor independent of physical activity level. The purpose of the present study was to investigate occupational sedentariness and breast cancer risk in pre- and postmenopausal women. In a population-based prospective cohort study (n = 29 524), working history was assessed by a questionnaire between 1990 and 1992. Participants were classified as having: (1) sedentary occupations only; (2) mixed occupations or (3) non-sedentary occupations only. The association between occupational sedentariness and breast cancer incidence was analyzed by Cox regression, adjusted for known risk factors and participation in competitive sports. Women with a working history of occupational sedentariness had a significantly increased risk of breast cancer (adjusted HR 1.20; 95% CI 1.05, 1.37) compared with those with mixed or non-sedentary occupations. The association was stronger among women younger than 55 years (adjusted HR 1.54; 95% CI 1.20, 1.96), whereas no association was seen in women 55 years or older. Adjustment for participation in competitive sports did not change the association. We found that occupational sedentariness was associated with increased breast cancer risk, especially in women younger than 55 years. This may be a modifiable risk factor by planning breaks during the working day. Whether this reduces the risk of breast cancer needs to be further studied.

Association of Competition Volume, Club Sports, and Sport Specialization With Sex and Lower Extremity Injury History in High School Athletes

PubMed Central

Post, Eric G.; Bell, David R.; Trigsted, Stephanie M.; Pfaller, Adam Y.; Hetzel, Scott J.; Brooks, M. Alison; McGuine, Timothy A.

2017-01-01

Background: High school athletes are increasingly encouraged to participate in 1 sport year-round to increase their sport skills. However, no study has examined the association of competition volume, club sport participation, and sport specialization with sex and lower extremity injury (LEI) in a large sample of high school athletes. Hypothesis: Increased competition volume, participating on a club team outside of school sports, and high levels of specialization will all be associated with a history of LEI. Girls will be more likely to engage in higher competition volume, participate on a club team, and be classified as highly specialized. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: High school athletes completed a questionnaire prior to the start of their competitive season regarding their sport participation and previous injury history. Multivariable logistic regression analyses were used to investigate associations of competition volume, club sport participation, and sport specialization with history of LEI, adjusting for sex. Results: A cohort of 1544 high school athletes (780 girls; grades 9-12) from 29 high schools completed the questionnaire. Girls were more likely to participate at high competition volume (23.2% vs 11.0%, χ2 = 84.7, P < 0.001), participate on a club team (61.2% vs 37.2%, χ2 = 88.3, P < 0.001), and be highly specialized (16.4% vs 10.4%, χ2 = 19.7, P < 0.001). Athletes with high competition volume, who participated in a club sport, or who were highly specialized had greater odds of reporting a previous LEI than those with low competition volume (odds ratio [OR], 2.08; 95% CI, 1.55-2.80; P < 0.001), no club sport participation (OR, 1.50; 95% CI, 1.20-1.88; P < 0.001), or low specialization (OR, 2.58; 95% CI, 1.88-3.54; P < 0.001), even after adjusting for sex. Conclusion: Participating in high sport volume, on a club team, or being highly specialized was associated with history of LEI. Girls were more likely to participate at high volumes, be active on club teams, or be highly specialized, potentially placing them at increased risk of injury. Clinical Relevance: Youth athletes, parents, and clinicians should be aware of the potential risks of intense, year-round participation in organized sports. PMID:28628419

Association of Competition Volume, Club Sports, and Sport Specialization With Sex and Lower Extremity Injury History in High School Athletes.

PubMed

Post, Eric G; Bell, David R; Trigsted, Stephanie M; Pfaller, Adam Y; Hetzel, Scott J; Brooks, M Alison; McGuine, Timothy A

High school athletes are increasingly encouraged to participate in 1 sport year-round to increase their sport skills. However, no study has examined the association of competition volume, club sport participation, and sport specialization with sex and lower extremity injury (LEI) in a large sample of high school athletes. Increased competition volume, participating on a club team outside of school sports, and high levels of specialization will all be associated with a history of LEI. Girls will be more likely to engage in higher competition volume, participate on a club team, and be classified as highly specialized. Cross-sectional study. Level 3. High school athletes completed a questionnaire prior to the start of their competitive season regarding their sport participation and previous injury history. Multivariable logistic regression analyses were used to investigate associations of competition volume, club sport participation, and sport specialization with history of LEI, adjusting for sex. A cohort of 1544 high school athletes (780 girls; grades 9-12) from 29 high schools completed the questionnaire. Girls were more likely to participate at high competition volume (23.2% vs 11.0%, χ 2 = 84.7, P < 0.001), participate on a club team (61.2% vs 37.2%, χ 2 = 88.3, P < 0.001), and be highly specialized (16.4% vs 10.4%, χ 2 = 19.7, P < 0.001). Athletes with high competition volume, who participated in a club sport, or who were highly specialized had greater odds of reporting a previous LEI than those with low competition volume (odds ratio [OR], 2.08; 95% CI, 1.55-2.80; P < 0.001), no club sport participation (OR, 1.50; 95% CI, 1.20-1.88; P < 0.001), or low specialization (OR, 2.58; 95% CI, 1.88-3.54; P < 0.001), even after adjusting for sex. Participating in high sport volume, on a club team, or being highly specialized was associated with history of LEI. Girls were more likely to participate at high volumes, be active on club teams, or be highly specialized, potentially placing them at increased risk of injury. Youth athletes, parents, and clinicians should be aware of the potential risks of intense, year-round participation in organized sports.

The impact of competition on quality and prices in the English care homes market

PubMed Central

Forder, Julien; Allan, Stephen

2014-01-01

This study assesses the impact of competition on quality and price in the English care/nursing homes market. Considering the key institutional features, we use a theoretical model to assess the conditions under which further competition could increase or reduce quality. A dataset comprising the population of 10,000 care homes was used. We constructed distance/travel-time weighted competition measures. Instrumental variable estimations, used to account for the endogeneity of competition, showed quality and price were reduced by greater competition. Further analyses suggested that the negative quality effect worked through the effect on price – higher competition reduces revenue which pushes down quality. PMID:24487075

The impact of competition on quality and prices in the English care homes market.

PubMed

Forder, Julien; Allan, Stephen

2014-03-01

This study assesses the impact of competition on quality and price in the English care/nursing homes market. Considering the key institutional features, we use a theoretical model to assess the conditions under which further competition could increase or reduce quality. A dataset comprising the population of 10,000 care homes was used. We constructed distance/travel-time weighted competition measures. Instrumental variable estimations, used to account for the endogeneity of competition, showed quality and price were reduced by greater competition. Further analyses suggested that the negative quality effect worked through the effect on price - higher competition reduces revenue which pushes down quality. Copyright © 2013 Elsevier B.V. All rights reserved.

Risk factors for shoulder pain and injury in swimmers: A critical systematic review.

PubMed

Hill, Lee; Collins, Malcolm; Posthumus, Michael

2015-11-01

Swimming is one of the most popular recreational and competitive sporting activities. In the 2013/2014 swimming season, 9630 men and 12,333 women were registered with the National Collegiate Athletics Association in the USA. The repetitive nature of the swimming stroke and demanding training programs of its athletes raises a number of concerns regarding incidence and severity of injuries that a swimmer might experience during a competitive season. A number of risk factors have previously been identified but the level of evidence from individual studies, as well as the level of certainty that these factors predispose a swimmer to pain and injury, to our knowledge has yet to be critically evaluated in a systematic review. Therefore, the primary objective of this review is to conduct a systematic review to critically assess the published evidence for risk factors that may predispose a swimmer to shoulder pain and injury. Three electronic databases, ScienceDirect, PubMed and SpringerLink, were searched using keywords "(Injury OR pain) AND (Swim*)" and "(Shoulder) AND (Swim*)". Based on the inclusion and exclusion criteria, 2731 unique titles were identified and were analyzed to a final 29 articles. Only articles with a level of evidence of I, II and III were included according to robust study design and data analysis. The level of certainty for each risk factor was determined. No studies were determined to have a high level of certainty, clinical joint laxity and instability, internal/external rotation, previous history of pain and injury and competitive level were determined to have a moderate level of certainty. All other risk factors were evaluated as having a low level of certainty. Although several risk factors were identified from the reviewed studies, prospective cohort studies, larger sample sizes, consistent and robust measures of risk should be employed in future research.

Modelling and predicting the simultaneous growth of Escherichia coli and lactic acid bacteria in milk.

PubMed

Ačai, P; Valík, L'; Medved'ová, A; Rosskopf, F

2016-09-01

Modelling and predicting the simultaneous competitive growth of Escherichia coli and starter culture of lactic acid bacteria (Fresco 1010, Chr. Hansen, Hørsholm, Denmark) was studied in milk at different temperatures and Fresco inoculum concentrations. The lactic acid bacteria (LAB) were able to induce an early stationary state in E. coli The developed model described and tested the growth inhibition of E. coli (with initial inoculum concentration 10(3) CFU/mL) when LAB have reached maximum density in different conditions of temperature (ranging from 12 ℃ to 30 ℃) and for various inoculum sizes of LAB (ranging from approximately 10(3) to 10(7) CFU/mL). The prediction ability of the microbial competition model (the Baranyi and Roberts model coupled with the Gimenez and Dalgaard model) was first performed only with parameters estimated from individual growth of E. coli and the LAB and then with the introduced competition coefficients evaluated from co-culture growth of E. coli and LAB in milk. Both the results and their statistical indices showed that the model with incorporated average values of competition coefficients improved the prediction of E. coli behaviour in co-culture with LAB. © The Author(s) 2015.

Risk, Reward, and Regulations: Reshaping the Financial Services Industry.

ERIC Educational Resources Information Center

Saul, Ralph S.

1984-01-01

Deregulation has had much to do with the competitive drive and vitality of financial services within the United States. The risks and rewards of deregulation for financial institutions are discussed, and principles which should serve as a guide in building any new regulatory structure are examined. (RM)

76 FR 60788 - Patient Protection and Affordable Care Act; Establishment of Exchanges and Qualified Health Plans...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-30

... for health insurance issuers related to reinsurance, risk corridors, and risk adjustment consistent... marketplaces for individuals and small employers to directly compare available private health insurance options... January 1, 2014, would help enhance competition in the health insurance market, improve choice of...

Oak mortality risk factors and mortality estimation

Treesearch

Stephen R. Shifley; Zhaofei Fan; John M. Kabrick; Randy G. Jensen

2006-01-01

Managers are often concerned about oak mortality in maturing mixed-oak forests, but they often lack explicit information about mortality risk for oaks that differ in species, size, crown class, competitive status, and growth rate. In eastern North America, tree species in the red oak group (Quercus Section Lobatae) are typically...

On the duration and intensity of cumulative advantage competitions

NASA Astrophysics Data System (ADS)

Jiang, Bo; Sun, Liyuan; Figueiredo, Daniel R.; Ribeiro, Bruno; Towsley, Don

2015-11-01

Network growth can be framed as a competition for edges among nodes in the network. As with various other social and physical systems, skill (fitness) and luck (random chance) act as fundamental forces driving competition dynamics. In the context of networks, cumulative advantage (CA)—the rich-get-richer effect—is seen as a driving principle governing the edge accumulation process. However, competitions coupled with CA exhibit non-trivial behavior and little is formally known about duration and intensity of CA competitions. By isolating two nodes in an ideal CA competition, we provide a mathematical understanding of how CA exacerbates the role of luck in detriment of skill. We show, for instance, that when nodes start with few edges, an early stroke of luck can place the less skilled in the lead for an extremely long period of time, a phenomenon we call ‘struggle of the fittest’. We prove that duration of a simple skill and luck competition model exhibit power-law tails when CA is present, regardless of skill difference, which is in sharp contrast to the exponential tails when fitness is distinct but CA is absent. We also prove that competition intensity is always upper bounded by an exponential tail, irrespective of CA and skills. Thus, CA competitions can be extremely long (infinite mean, depending on fitness ratio) but almost never very intense. The theoretical results are corroborated by extensive numerical simulations. Our findings have important implications to competitions not only among nodes in networks but also in contexts that leverage socio-physical models embodying CA competitions.

Contrasting the effects of environment, dispersal and biotic interactions to explain the distribution of invasive plants in alpine communities

PubMed Central

GALLIEN, Laure; MAZEL, Florent; LAVERGNE, Sébastien; RENAUD, Julien; DOUZET, Rolland; THUILLER, Wilfried

2015-01-01

Despite considerable efforts devoted to investigate the community assembly processes driving plant invasions, few general conclusions have been drawn so far. Three main processes, generally acting as successive filters, are thought to be of prime importance. The invader has to disperse (1st filter) into a suitable environment (2nd filter) and succeed in establishing in recipient communities through competitive interactions (3rd filter) using two strategies: competition avoidance by the use of different resources (resource opportunity), or competitive exclusion of native species. Surprisingly, despite the general consensus on the importance of investigating these three processes and their interplay, they are usually studied independently. Here we aim to analyse these three filters together, by including them all: abiotic environment, dispersal and biotic interactions, into models of invasive species distributions. We first propose a suite of indices (based on species functional dissimilarities) supposed to reflect the two competitive strategies (resource opportunity and competition exclusion). Then, we use a set of generalised linear models to explain the distribution of seven herbaceous invaders in natural communities (using a large vegetation database for the French Alps containing 5,000 community-plots). Finally, we measure the relative importance of competitive interaction indices, identify the type of coexistence mechanism involved and how this varies along environmental gradients. Adding competition indices significantly improved model’s performance, but neither resource opportunity nor competitive exclusion were common strategies among the seven species. Overall, we show that combining environmental, dispersal and biotic information to model invasions has excellent potential for improving our understanding of invader success. PMID:26290653

Dynamics of multiple infection and within-host competition by the anther-smut pathogen.

PubMed

Hood, M E

2003-07-01

Infection of one host by multiple pathogen genotypes represents an important area of pathogen ecology and evolution that lacks a broad empirical foundation. Multiple infection of Silene latifolia by Microbotryum violaceum was studied under field and greenhouse conditions using the natural polymorphism for mating-type bias as a marker. Field transmission resulted in frequent multiple infection, and each stem of the host was infected independently. Within-host diversity of infections equaled that of nearby inoculum sources by the end of the growing season. The number of diseased stems per plant was positively correlated with multiple infection and with overwintering mortality. As a result, multiply infected plants were largely purged from the population, and there was lower within-host pathogen diversity in the second season. However, among plants with a given number of diseased stems, multiply infected plants had a lower risk of overwintering mortality. Following simultaneous and sequential inoculation, strong competitive exclusion was demonstrated, and the first infection had a significant advantage. Dynamics of multiple infection initially included components of coinfection models for virulence evolution and then components of superinfection models after systemic colonization. Furthermore, there was evidence for an advantage of genotypes with mating-type bias, which may contribute to maintenance of this polymorphism in natural populations.

An integrated new product development framework - an application on green and low-carbon products

NASA Astrophysics Data System (ADS)

Lin, Chun-Yu; Lee, Amy H. I.; Kang, He-Yau

2015-03-01

Companies need to be innovative to survive in today's competitive market; thus, new product development (NPD) has become very important. This research constructs an integrated NPD framework for developing new products. In stage one, customer attributes (CAs) and engineering characteristics (ECs) for developing products are collected, and fuzzy interpretive structural modelling (FISM) is applied to understand the relationships among these critical factors. Based on quality function deployment (QFD), a house of quality is then built, and fuzzy analytic network process (FANP) is adopted to calculate the relative importance of ECs. In stage two, fuzzy failure mode and effects analysis (FFMEA) is applied to understand the potential failures of the ECs and to determine the importance of ECs with respect to risk control. In stage three, a goal programming (GP) model is constructed to consider the outcome from the FANP-QFD, FFMEA and other objectives, in order to select the most important ECs. Due to pollution and global warming, environmental protection has become an important topic. With both governments and consumers developing environmental consciousness, successful green and low-carbon NPD provides an important competitive advantage, enabling the survival or renewal of firms. The proposed framework is implemented in a panel manufacturing firm for designing a green and low-carbon product.

Health Risk Factors Associated with Acute Respiratory Illness Among U.S. Army Recruits Attending Basic Combat Training

DTIC Science & Technology

2012-06-11

Competitive athletes recognize peak performance on the field requires consistent intense practice off the field. Recreational sports enthusiasts to Olympic...challenging as a first time marathon runner. Recreational runners tend to run at comfortable distances and intensities, competitive athletes...level of aerobic fitness, as reflected by poor performance on the initial one-mile run test, may experience increased ARI incidence as 3   a result

NASA's Space Launch System Advanced Booster Engineering Demonstration and/or Risk Reduction Efforts

NASA Technical Reports Server (NTRS)

Crumbly, Christopher M.; Dumbacher, Daniel L.; May, Todd A.

2012-01-01

The National Aeronautics and Space Administration (NASA) formally initiated the Space Launch System (SLS) development in September 2011, with the approval of the program s acquisition plan, which engages the current workforce and infrastructure to deliver an initial 70 metric ton (t) SLS capability in 2017, while using planned block upgrades to evolve to a full 130 t capability after 2021. A key component of the acquisition plan is a three-phased approach for the first stage boosters. The first phase is to complete the development of the Ares and Space Shuttle heritage 5-segment solid rocket boosters (SRBs) for initial exploration missions in 2017 and 2021. The second phase in the booster acquisition plan is the Advanced Booster Risk Reduction and/or Engineering Demonstration NASA Research Announcement (NRA), which was recently awarded after a full and open competition. The NRA was released to industry on February 9, 2012, with a stated intent to reduce risks leading to an affordable advanced booster and to enable competition. The third and final phase will be a full and open competition for Design, Development, Test, and Evaluation (DDT&E) of the advanced boosters. There are no existing boosters that can meet the performance requirements for the 130 t class SLS. The expected thrust class of the advanced boosters is potentially double the current 5-segment solid rocket booster capability. These new boosters will enable the flexible path approach to space exploration beyond Earth orbit (BEO), opening up vast opportunities including near-Earth asteroids, Lagrange Points, and Mars. This evolved capability offers large volume for science missions and payloads, will be modular and flexible, and will be right-sized for mission requirements. NASA developed the Advanced Booster Engineering Demonstration and/or Risk Reduction NRA to seek industry participation in reducing risks leading to an affordable advanced booster that meets the SLS performance requirements. Demonstrations and/or risk reduction efforts were required to be related to a proposed booster concept directly applicable to fielding an advanced booster. This paper will discuss, for the first time publicly, the contract awards and how NASA intends to use the data from these efforts to prepare for the planned advanced booster DDT&E acquisition as the SLS Program moves forward with competitively procured affordable performance enhancements.

NASA's Space Launch System Advanced Booster Engineering Demonstration and Risk Reduction Efforts

NASA Technical Reports Server (NTRS)

Crumbly, Christopher M.; May, Todd; Dumbacher, Daniel

2012-01-01

The National Aeronautics and Space Administration (NASA) formally initiated the Space Launch System (SLS) development in September 2011, with the approval of the program s acquisition plan, which engages the current workforce and infrastructure to deliver an initial 70 metric ton (t) SLS capability in 2017, while using planned block upgrades to evolve to a full 130 t capability after 2021. A key component of the acquisition plan is a three-phased approach for the first stage boosters. The first phase is to complete the development of the Ares and Space Shuttle heritage 5-segment solid rocket boosters for initial exploration missions in 2017 and 2021. The second phase in the booster acquisition plan is the Advanced Booster Risk Reduction and/or Engineering Demonstration NASA Research Announcement (NRA), which was recently awarded after a full and open competition. The NRA was released to industry on February 9, 2012, and its stated intent was to reduce risks leading to an affordable Advanced Booster and to enable competition. The third and final phase will be a full and open competition for Design, Development, Test, and Evaluation (DDT&E) of the Advanced Boosters. There are no existing boosters that can meet the performance requirements for the 130 t class SLS. The expected thrust class of the Advanced Boosters is potentially double the current 5-segment solid rocket booster capability. These new boosters will enable the flexible path approach to space exploration beyond Earth orbit, opening up vast opportunities including near-Earth asteroids, Lagrange Points, and Mars. This evolved capability offers large volume for science missions and payloads, will be modular and flexible, and will be right-sized for mission requirements. NASA developed the Advanced Booster Engineering Demonstration and/or Risk Reduction NRA to seek industry participation in reducing risks leading to an affordable Advanced Booster that meets the SLS performance requirements. Demonstrations and/or risk reduction efforts were required to be related to a proposed booster concept directly applicable to fielding an Advanced Booster. This paper will discuss, for the first time publicly, the contract awards and how NASA intends to use the data from these efforts to prepare for the planned Advanced Booster DDT&E acquisition as the SLS Program moves forward with competitively procured affordable performance enhancements.

Evaluation of wholesale electric power market rules and financial risk management by agent-based simulations

NASA Astrophysics Data System (ADS)

Yu, Nanpeng

As U.S. regional electricity markets continue to refine their market structures, designs and rules of operation in various ways, two critical issues are emerging. First, although much experience has been gained and costly and valuable lessons have been learned, there is still a lack of a systematic platform for evaluation of the impact of a new market design from both engineering and economic points of view. Second, the transition from a monopoly paradigm characterized by a guaranteed rate of return to a competitive market created various unfamiliar financial risks for various market participants, especially for the Investor Owned Utilities (IOUs) and Independent Power Producers (IPPs). This dissertation uses agent-based simulation methods to tackle the market rules evaluation and financial risk management problems. The California energy crisis in 2000-01 showed what could happen to an electricity market if it did not go through a comprehensive and rigorous testing before its implementation. Due to the complexity of the market structure, strategic interaction between the participants, and the underlying physics, it is difficult to fully evaluate the implications of potential changes to market rules. This dissertation presents a flexible and integrative method to assess market designs through agent-based simulations. Realistic simulation scenarios on a 225-bus system are constructed for evaluation of the proposed PJM-like market power mitigation rules of the California electricity market. Simulation results show that in the absence of market power mitigation, generation company (GenCo) agents facilitated by Q-learning are able to exploit the market flaws and make significantly higher profits relative to the competitive benchmark. The incorporation of PJM-like local market power mitigation rules is shown to be effective in suppressing the exercise of market power. The importance of financial risk management is exemplified by the recent financial crisis. In this dissertation, basic financial risk management concepts relevant for wholesale electric power markets are carefully explained and illustrated. In addition, the financial risk management problem in wholesale electric power markets is generalized as a four-stage process. Within the proposed financial risk management framework, the critical problem of financial bilateral contract negotiation is addressed. This dissertation analyzes a financial bilateral contract negotiation process between a generating company and a load-serving entity in a wholesale electric power market with congestion managed by locational marginal pricing. Nash bargaining theory is used to model a Pareto-efficient settlement point. The model predicts negotiation results under varied conditions and identifies circumstances in which the two parties might fail to reach an agreement. Both analysis and agent-based simulation are used to gain insight regarding how relative risk aversion and biased price estimates influence negotiated outcomes. These results should provide useful guidance to market participants in their bilateral contract negotiation processes.

How direct competition shapes coexistence and vaccine effects in multi-strain pathogen systems.

PubMed

Gjini, Erida; Valente, Carina; Sá-Leão, Raquel; Gomes, M Gabriela M

2016-01-07

We describe an integrated modeling framework for understanding strain coexistence in polymorphic pathogen systems. Previous studies have debated the utility of neutral formulations and focused on cross-immunity between strains as a major stabilizing mechanism. Here we convey that direct competition for colonization mediates stable coexistence only when competitive abilities amongst pathogen clones satisfy certain pairwise asymmetries. We illustrate our ideas with nested SIS models of single and dual colonization, applied to polymorphic pneumococcal bacteria. By fitting the models to cross-sectional prevalence data from Portugal (before and after the introduction of a seven-valent pneumococcal conjugate vaccine), we are able to not only statistically compare neutral and non-neutral epidemiological formulations, but also estimate vaccine efficacy, transmission and competition parameters simultaneously. Our study highlights that the response of polymorphic pathogen populations to interventions holds crucial information about strain interactions, which can be extracted by suitable nested modeling. Copyright © 2015 Elsevier Ltd. All rights reserved.

Towards Automated Bargaining in Electronic Markets: A Partially Two-Sided Competition Model

NASA Astrophysics Data System (ADS)

Gatti, Nicola; Lazaric, Alessandro; Restelli, Marcello

This paper focuses on the prominent issue of automating bargaining agents within electronic markets. Models of bargaining in literature deal with settings wherein there are only two agents and no model satisfactorily captures settings in which there is competition among buyers, being they more than one, and analogously among sellers. In this paper, we extend the principal bargaining protocol, i.e. the alternating-offers protocol, to capture bargaining in markets. The model we propose is such that, in presence of a unique buyer and a unique seller, agents' equilibrium strategies are those in the original protocol. Moreover, we game theoretically study the considered game providing the following results: in presence of one-sided competition (more buyers and one seller or vice versa) we provide agents' equilibrium strategies for all the values of the parameters, in presence of two-sided competition (more buyers and more sellers) we provide an algorithm that produce agents' equilibrium strategies for a large set of the parameters and we experimentally evaluate its effectiveness.

Principals of Design for High Performing Organizations: A Suggested Research Program. Appendixes

DTIC Science & Technology

1994-03-01

keiretsu are subjected to the measure of the market and the sting of competition . The Japanese model combines fierce internal competition with a...reasonable that such a quasi-market can exploit the benefits of competition and price signals to provide internal customers with better service at a...system. Would the restriction of market entry necessarily lead to monopolistic competition that ends up extracting unnecessary rents from captive

Simulated Warming Differentially Affects the Growth and Competitive Ability of Centaurea maculosa Populations from Home and Introduced Ranges

PubMed Central

He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao

2012-01-01

Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range) and North America (introduced range) under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors. PMID:22303485

Simulated warming differentially affects the growth and competitive ability of Centaurea maculosa populations from home and introduced ranges.

PubMed

He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao

2012-01-01

Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range) and North America (introduced range) under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors.

Injury trends in sanctioned mixed martial arts competition: a 5-year review from 2002 to 2007.

PubMed

Ngai, K M; Levy, F; Hsu, E B

2008-08-01

Professional mixed martial arts (MMA) competition is a full-contact sport that has risen rapidly in popularity in recent years. However, there is limited information regarding the incidence of competition injuries after sanctioning by an athletic commission. We conducted a retrospective cohort study to examine MMA injury patterns during a 5 year period after sanctioning in the state of Nevada. Data from all regulated MMA competitions during the study period from March 2002 to September 2007 (1270 fight exposures) was obtained. Injury odds ratios were calculated by conditional logistic regression on match outcome, age, weight, and fight experience, using a pair-matched case-control design (n = 464) and by multiple logistic regression on match outcome, age, fight experience, weight, combat minutes, and scheduled rounds. During the 635 professional MMA matches, 300 of the 1270 athletes sustained documented injuries with an injury rate of 23.6 per 100 fight participations. Most common reported injuries were lacerations and upper limb injuries. Severe concussion rate was 15.4 per 1000 athlete exposures, or 3% of all matches. No deaths or critical sports-related injuries resulted from any of the regulated matches during the study period. Age, weight and fight experience did not statistically increase the likelihood of injuries after controlling for other covariates. Injury rates in regulated professional MMA competition are similar to other combat sports; the overall risk of critical sports-related injury seems to be low. Additional study is warranted to achieve a better understanding of injury trends and ways to further lower injury risk in MMA.

Ovarian fluid of receptive females enhances sperm velocity

NASA Astrophysics Data System (ADS)

Gasparini, Clelia; Andreatta, Gabriele; Pilastro, Andrea

2012-05-01

The females of several internal fertilizers are able to store sperm for a long time, reducing the risk of sperm limitation. However, it also means that males can attempt to mate outside females' receptive period, potentially increasing the level of sperm competition and exacerbating sexual conflict over mating. The guppy ( Poecilia reticulata), an internally fertilizing fish, is a model system of such competition and conflict. Female guppies accept courtship and mate consensually only during receptive periods of the ovarian cycle but receive approximately one (mostly forced) mating attempt per minute both during and outside their sexually receptive phase. In addition, females can store viable sperm for months. We expected that guppy females would disfavour sperm received during their unreceptive period, possibly by modulating the quality and/or quantity of the components present in the ovarian fluid (OF) over the breeding cycle. Ovarian fluid has been shown to affect sperm velocity, a determinant of sperm competition success in this and other fishes. We found that in vitro sperm velocity is slower in OF collected from unreceptive females than in OF from receptive females. Visual stimulation with a potential partner prior to collection did not significantly affect in vitro sperm velocity. These results suggest that sperm received by unreceptive females may be disfavoured as sperm velocity likely affects the migration process and the number of sperm that reach storage sites.

A solution to the biodiversity paradox by logical deterministic cellular automata.

PubMed

Kalmykov, Lev V; Kalmykov, Vyacheslav L

2015-06-01

The paradox of biological diversity is the key problem of theoretical ecology. The paradox consists in the contradiction between the competitive exclusion principle and the observed biodiversity. The principle is important as the basis for ecological theory. On a relatively simple model we show a mechanism of indefinite coexistence of complete competitors which violates the known formulations of the competitive exclusion principle. This mechanism is based on timely recovery of limiting resources and their spatio-temporal allocation between competitors. Because of limitations of the black-box modeling there was a problem to formulate the exclusion principle correctly. Our white-box multiscale model of two-species competition is based on logical deterministic individual-based cellular automata. This approach provides an automatic deductive inference on the basis of a system of axioms, and gives a direct insight into mechanisms of the studied system. It is one of the most promising methods of artificial intelligence. We reformulate and generalize the competitive exclusion principle and explain why this formulation provides a solution of the biodiversity paradox. In addition, we propose a principle of competitive coexistence.

The list-strength effect in recall: relative-strength competition and retrieval inhibition may both contribute to forgetting.

PubMed

Verde, Michael F

2009-01-01

According to the principle of relative-strength competition, stronger items in memory block the retrieval of weaker items. This principle, integral to many theories of forgetting over the years, derives much of its support from the list-strength effect (LSE), in which strengthening some items in a study list makes it more difficult to recall other items. Work in the retrieval-induced forgetting literature has challenged the existence of relative-strength competition, 1st by offering many examples of a null LSE and 2nd by proposing that extant observations of the LSE can be explained by retrieval inhibition. In the present study, a series of experiments produced a robust LSE in cued recall under conditions meant to control the contribution of retrieval inhibition. Simulations of the SAM-REM model of recall (K. J. Malmberg & R. M. Shiffrin, 2005) showed that a model based on relative-strength competition can accommodate both the presence and absence of an LSE. The empirical results and model simulations together make a case for the role of strength-based competition in forgetting.

Competition favors elk over beaver in a riparian willow ecosystem

USGS Publications Warehouse

Baker, B.W.; Peinetti, H.R.; Coughenour, M.C.; Johnson, T.L.

2012-01-01

Beaver (Castor spp.) conservation requires an understanding of their complex interactions with competing herbivores. Simulation modeling offers a controlled environment to examine long-term dynamics in ecosystems driven by uncontrollable variables. We used a new version of the SAVANNA ecosystem model to investigate beaver (C. Canadensis) and elk (Cervus elapses) competition for willow (Salix spp.). We initialized the model with field data from Rocky Mountain National Park, Colorado, USA, to simulate a 4-ha riparian ecosystem containing beaver, elk, and willow. We found beaver persisted indefinitely when elk density was or = 30 elk km_2. The loss of tall willow preceded rapid beaver declines, thus willow condition may predict beaver population trajectory in natural environments. Beaver were able to persist with slightly higher elk densities if beaver alternated their use of foraging sites in a rest-rotation pattern rather than maintained continuous use. Thus, we found asymmetrical competition for willow strongly favored elk over beaver in a simulated montane ecosystem. Finally, we discuss application of the SAVANNA model and mechanisms of competition relative to beaver persistence as metapopulations, ecological resistance and alternative state models, and ecosystem regulation.

Perception of Health Problems Among Competitive Runners

PubMed Central

Jelvegård, Sara; Timpka, Toomas; Bargoria, Victor; Gauffin, Håkan; Jacobsson, Jenny

2016-01-01

Background: Approximately 2 of every 3 competitive runners sustain at least 1 health problem each season. Most of these problems are nontraumatic injuries with gradual onset. The main known risk indicator for sustaining a new running-related injury episode is a history of a previous injury, suggesting that behavioral habits are part of the causal mechanisms. Purpose: Identification of elements associated with purposeful interpretations of body perceptions and balanced behavioral responses may supply vital information for prevention of health problems in runners. This study set out to explore competitive runners’ cognitive appraisals of perceived symptoms on injury and illness and how these appraisals are transformed into behavior. Study Design: Cross-sectional study; Level of evidence, 3. Methods: The study population consisted of Swedish middle- and long-distance runners from the national top 15 list. Qualitative research methods were used to categorize interview data and perform a thematic analysis. The categories resulting from the analysis were used to construct an explanatory model. Results: Saturation of the thematic classification required that data from 8 male and 6 female runners (age range, 20-36 years) were collected. Symptoms interpreted to be caused by illness or injury with a sudden onset were found to lead to immediate action and changes to training and competition programs (activity pacing). In contrast, perceptions interpreted to be due to injuries with gradual onset led to varied behavioral reactions. These behavioral responses were planned with regard to short-term consequences and were characterized by indifference and neglect of long-term implications, consistent with an overactivity behavioral pattern. The latter pattern was consistent with a psychological adaptation to stimuli that is presented progressively to the athlete. Conclusion: Competitive runners appraise whether a health problem requires immediate withdrawal from training based on whether the problem is interpreted as an illness and/or has a sudden onset. The ensuing behaviors follow 2 distinct patterns that can be termed “activity pacing” and “overactivity.” PMID:28210643

Plants may alter competition by modifying nutrient bioavailability in rhizosphere: a modeling approach.

PubMed

Raynaud, Xavier; Jaillard, Benoît; Leadley, Paul W

2008-01-01

Plants modify nutrient availability by releasing chemicals in the rhizosphere. This change in availability induced by roots (bioavailability) is known to improve nutrient uptake by individual plants releasing such compounds. Can this bioavailability alter plant competition for nutrients and under what conditions? To address these questions, we have developed a model of nutrient competition between plant species based on mechanistic descriptions of nutrient diffusion, plant exudation, and plant uptake. The model was parameterized using data of the effects of root citrate exudation on phosphorus availability. We performed a sensitivity analysis for key parameters to test the generality of these effects. Our simulations suggest the following. (1) Nutrient uptake depends on the number of roots when nutrients and exudates diffuse little, because individual roots are nearly independent in terms of nutrient supply. In this case, bioavailability profits only species with exudates. (2) Competition for nutrients depends on the spatial arrangement of roots when nutrients diffuse little but exudates diffuse widely. (3) Competition for nutrients depends on the nutrient uptake capacity of roots when nutrients and exudates diffuse widely. In this case, bioavailability profits all species. Mechanisms controlling competition for bioavailable nutrients appear to be diverse and strongly depend on soil, nutrient, and plant properties.

The role of competition – colonization tradeoffs and spatial heterogeneity in promoting trematode coexistence

USGS Publications Warehouse

Mordecai, Erin A.; Jaramillo, Alejandra G.; Ashford, Jacob E.; Hechinger, Ryan F.; Lafferty, Kevin D.

2016-01-01

Competition – colonization tradeoffs occur in many systems, and theory predicts that they can strongly promote species coexistence. However, there is little empirical evidence that observed competition – colonization tradeoffs are strong enough to maintain diversity in natural systems. This is due in part to a mismatch between theoretical assumptions and biological reality in some systems. We tested whether a competition – colonization tradeoff explains how a diverse trematode guild coexists in California horn snail populations, a system that meets the requisite criteria for the tradeoff to promote coexistence. A field experiment showed that subordinate trematode species tended to have higher colonization rates than dominant species. This tradeoff promoted coexistence in parameterized models but did not fully explain trematode diversity and abundance, suggesting a role of additional diversity maintenance mechanisms. Spatial heterogeneity is an alternative way to promote coexistence if it isolates competing species. We used scale transition theory to expand the competition – colonization tradeoff model to include spatial variation. The parameterized model showed that spatial variation in trematode prevalence did not isolate most species sufficiently to explain the overall high diversity, but could benefit some rare species. Together, the results suggest that several mechanisms combine to maintain diversity, even when a competition – colonization tradeoff occurs.

A Study on Standard Competition with Network Effect Based on Evolutionary Game Model

NASA Astrophysics Data System (ADS)

Wang, Ye; Wang, Bingdong; Li, Kangning

Owing to networks widespread in modern society, standard competition with network effect is now endowed with new connotation. This paper aims to study the impact of network effect on standard competition; it is organized in the mode of "introduction-model setup-equilibrium analysis-conclusion". Starting from a well-structured model of evolutionary game, it is then extended to a dynamic analysis. This article proves both theoretically and empirically that whether or not a standard can lead the market trends depends on the utility it would bring, and the author also discusses some advisable strategies revolving around the two factors of initial position and border break.

Mean field dynamics of the coexistence phase in generalized cyclic competitions

NASA Astrophysics Data System (ADS)

Mowlaei, Shahir; Roman, Ahmed; Pleimling, Michel

2014-03-01

Multispecies Lotka-Volterra models have been a rich source of inspiration in multidisciplinary areas of research due to their inherent nonlinearity which yields intriguing and complex behavior for a large class of competition schemes. Of particular interest here is a subclass of these models where competition is realized in a cyclic manner through a variety of reactions. The goal is to predict and quantify emerging two-dimensional patterns in the coexistence regime. The focus will further be on a set of models that can be analyzed without using the cumbersome machinery of slow-manifolds. This work is supported by the US National Science Foundation through grant DMR-1205309.

Cross-disciplinary problem-solving workshop: a pedagogical approach to anticipate ergonomist engineering design collaboration.

PubMed

Brunier, Elisabeth; Le Chapellier, Michel; Dejean, Pierre Henri

2012-01-01

The aims of this paper are to present concept and results of an innovative educational model approach based on ergonomics involvement in industrial project. First we present Cross disciplinary Problem solving Workshop by answering three questions:1) What is a CPW: A partnership between Universities and one or several companies, purposes of it are first to increase health, well being, companies teams competencies, and competitiveness, second to train the "IPOD generation" to include risks prevention in design. 2) How does it work? CPW allows cooperation between experience and new insight through inductive methods. This model follows the Piaget (1) philosophy linking concrete world to abstraction by a learning system associating realization and abstraction. 3) Is it successful? In order to answer this third question we will show examples of studies and models performed during CPWs.It appears that the CPWs produce visible results in companies such as new process designs, new methods, and also changes in lectures. However some less visible results remain unclear: How the company personnel evolve during and after CPW? Does CPW motivate our future engineers enough to continuously improve their skills in risk prevention and innovative design?

Sexually selected sex differences in competitiveness explain sex differences in changes in drinking game participation.

PubMed

Hone, Liana S E; McCullough, Michael

2015-05-14

Drinking games are a risk factor for behavioral and health problems among university students. Previous cross-sectional research by Hone, Carter, and McCullough (2013) replicated well-established sex differences in drinking game behaviors (i.e., that men are more active drinking game participants than are women) and university drinking problems more generally. Hone et al. (2013) also found that these male-specific behavioral patterns are attributable in part to the fact that men's generally unrestricted sexual strategies, plus their social competitiveness, motivate them to participate in drinking games to display their fortitude and compete with same-sex rivals. Here, the authors conducted a study to evaluate with greater causal rigor whether sex differences in sexual restrictedness and social competitiveness-and sex differences in motivations for participating in drinking games in particular-are partially responsible for the sex differences in university students' drinking game behaviors and drinking problems. Sex differences in changes in frequency of drinking game participation were partially mediated by competitive motivations for participating in drinking games and by the effects of social competitiveness on competitive drinking game motivation. These findings lend additional support to the proposition that participation in drinking games is motivated in part by their suitability as a venue for sexual competition in university students' day-to-day lives.

Examining Competition in Ontario's Higher Education Market

ERIC Educational Resources Information Center

Farhan, Bayan Yousef

2017-01-01

Financial challenges have forced many publicly funded academic institutions in Ontario to adopt a corporate model and to use market tools to compete in the higher education market and maintain their enrolment and revenue levels. This study has analyzed how competition affects publicly funded universities in Ontario. Competition was examined by…

Nonlinear analysis of the heartbeats in public patient ECGs using an automated PD2i algorithm for risk stratification of arrhythmic death

PubMed Central

Skinner, James E; Anchin, Jerry M; Weiss, Daniel N

2008-01-01

Heart rate variability (HRV) reflects both cardiac autonomic function and risk of arrhythmic death (AD). Reduced indices of HRV based on linear stochastic models are independent risk factors for AD in post-myocardial infarct cohorts. Indices based on nonlinear deterministic models have a significantly higher sensitivity and specificity for predicting AD in retrospective data. A need exists for nonlinear analytic software easily used by a medical technician. In the current study, an automated nonlinear algorithm, the time-dependent point correlation dimension (PD2i), was evaluated. The electrocardiogram (ECG) data were provided through an National Institutes of Health-sponsored internet archive (PhysioBank) and consisted of all 22 malignant arrhythmia ECG files (VF/VT) and 22 randomly selected arrhythmia files as the controls. The results were blindly calculated by automated software (Vicor 2.0, Vicor Technologies, Inc., Boca Raton, FL) and showed all analyzable VF/VT files had PD2i < 1.4 and all analyzable controls had PD2i > 1.4. Five VF/VT and six controls were excluded because surrogate testing showed the RR-intervals to contain noise, possibly resulting from the low digitization rate of the ECGs. The sensitivity was 100%, specificity 85%, relative risk > 100; p < 0.01, power > 90%. Thus, automated heartbeat analysis by the time-dependent nonlinear PD2i-algorithm can accurately stratify risk of AD in public data made available for competitive testing of algorithms. PMID:18728829

Root-shoot growth responses during interspecific competition quantified using allometric modelling.

PubMed

Robinson, David; Davidson, Hazel; Trinder, Clare; Brooker, Rob

2010-12-01

Plant competition studies are restricted by the difficulty of quantifying root systems of competitors. Analyses are usually limited to above-ground traits. Here, a new approach to address this issue is reported. Root system weights of competing plants can be estimated from: shoot weights of competitors; combined root weights of competitors; and slopes (scaling exponents, α) and intercepts (allometric coefficients, β) of ln-regressions of root weight on shoot weight of isolated plants. If competition induces no change in root : shoot growth, α and β values of competing and isolated plants will be equal. Measured combined root weight of competitors will equal that estimated allometrically from measured shoot weights of each competing plant. Combined root weights can be partitioned directly among competitors. If, as will be more usual, competition changes relative root and shoot growth, the competitors' combined root weight will not equal that estimated allometrically and cannot be partitioned directly. However, if the isolated-plant α and β values are adjusted until the estimated combined root weight of competitors matches the measured combined root weight, the latter can be partitioned among competitors using their new α and β values. The approach is illustrated using two herbaceous species, Dactylis glomerata and Plantago lanceolata. Allometric modelling revealed a large and continuous increase in the root : shoot ratio by Dactylis, but not Plantago, during competition. This was associated with a superior whole-plant dry weight increase in Dactylis, which was ultimately 2·5-fold greater than that of Plantago. Whole-plant growth dominance of Dactylis over Plantago, as deduced from allometric modelling, occurred 14-24 d earlier than suggested by shoot data alone. Given reasonable assumptions, allometric modelling can analyse competitive interactions in any species mixture, and overcomes a long-standing problem in studies of competition.

Risk Factors for Social Networking Site Scam Victimization Among Malaysian Students.

PubMed

Kirwan, Gráinne H; Fullwood, Chris; Rooney, Brendan

2018-02-01

Social networking sites (SNSs) can provide cybercriminals with various opportunities, including gathering of user data and login credentials to enable fraud, and directing of users toward online locations that may install malware onto their devices. The techniques employed by such cybercriminals can include clickbait (text or video), advertisement of nonexistent but potentially desirable products, and hoax competitions/giveaways. This study aimed to identify risk factors associated with falling victim to these malicious techniques. An online survey was completed by 295 Malaysian undergraduate students, finding that more than one-third had fallen victim to SNS scams. Logistic regression analysis identified several victimization risk factors including having higher scores in impulsivity (specifically cognitive complexity), using fewer devices for SNSs, and having been on an SNS for a longer duration. No reliable model was found for vulnerability to hoax valuable gift giveaways and "friend view application" advertising specifically, but vulnerability to video clickbait was predicted by lower extraversion scores, higher levels of openness to experience, using fewer devices, and being on an SNS for a longer duration. Other personality traits were not associated with either overall victimization susceptibility or increased risk of falling victim to the specific techniques. However, age approached significance within both the video clickbait and overall victimization models. These findings suggest that routine activity theory may be particularly beneficial in understanding and preventing SNSs scam victimization.

The relation between proactive environmental strategies and competitive advantage

NASA Astrophysics Data System (ADS)

Butnariu, A.; Avasilcăi, S.

2015-11-01

There are two distinct orientations of the environmental management that companies may adopt: the model of compliance and the strategic model. The strategic model treats environmental expenses as investments that will lead to competitive advantage for the company. Nevertheless, there are few scientific works that prove the relation between corporate environmental investments and competitive advantage. Thereby, in order to bring clarifications about the profound implications of environmental investments, in the first stage of our research we have proposed the hypothesis that the environmental investments would probably lead to competitive advantage by creating capabilities that are mediators of this relation. In the second stage we have tested this hypothesis, using the research method of survey. A questionnaire was sent to managers in textile Romanian industry, and 109 answers were received. The data was analysed using the linear multiple regression method and the results confirm our hypothesis.

The discrete dynamics of symmetric competition in the plane.

PubMed

Jiang, H; Rogers, T D

1987-01-01

We consider the generalized Lotka-Volterra two-species system xn + 1 = xn exp(r1(1 - xn) - s1yn) yn + 1 = yn exp(r2(1 - yn) - s2xn) originally proposed by R. M. May as a model for competitive interaction. In the symmetric case that r1 = r2 and s1 = s2, a region of ultimate confinement is found and the dynamics therein are described in some detail. The bifurcations of periodic points of low period are studied, and a cascade of period-doubling bifurcations is indicated. Within the confinement region, a parameter region is determined for the stable Hopf bifurcation of a pair of symmetrically placed period-two points, which imposes a second component of oscillation near the stable cycles. It is suggested that the symmetric competitive model contains much of the dynamical complexity to be expected in any discrete two-dimensional competitive model.

The role of adaptations in two-strain competition for sylvatic Trypanosoma cruzi transmission.

PubMed

Kribs-Zaleta, Christopher M; Mubayi, Anuj

2012-01-01

This study presents a continuous-time model for the sylvatic transmission dynamics of two strains of Trypanosoma cruzi enzootic in North America, in order to study the role that adaptations of each strain to distinct modes of transmission (classical stercorarian transmission on the one hand, and vertical and oral transmission on the other) may play in the competition between the two strains. A deterministic model incorporating contact process saturation predicts competitive exclusion, and reproductive numbers for the infection provide a framework for evaluating the competition in terms of adaptive trade-off between distinct transmission modes. Results highlight the importance of oral transmission in mediating the competition between horizontal (stercorarian) and vertical transmission; its presence as a competing contact process advantages vertical transmission even without adaptation to oral transmission, but such adaptation appears necessary to explain the persistence of (vertically-adapted) T. cruzi IV in raccoons and woodrats in the southeastern United States.

Stochastic competitive learning in complex networks.

PubMed

Silva, Thiago Christiano; Zhao, Liang

2012-03-01

Competitive learning is an important machine learning approach which is widely employed in artificial neural networks. In this paper, we present a rigorous definition of a new type of competitive learning scheme realized on large-scale networks. The model consists of several particles walking within the network and competing with each other to occupy as many nodes as possible, while attempting to reject intruder particles. The particle's walking rule is composed of a stochastic combination of random and preferential movements. The model has been applied to solve community detection and data clustering problems. Computer simulations reveal that the proposed technique presents high precision of community and cluster detections, as well as low computational complexity. Moreover, we have developed an efficient method for estimating the most likely number of clusters by using an evaluator index that monitors the information generated by the competition process itself. We hope this paper will provide an alternative way to the study of competitive learning..

Hostile sexism (de)motivates women's social competition intentions: The contradictory role of emotions.

PubMed

Lemonaki, Elena; Manstead, Antony S R; Maio, Gregory R

2015-09-01

In the present research, we examine the ways in which exposure to hostile sexism influences women's competitive collective action intentions. Prior to testing our main model, our first study experimentally induced high versus low levels of security-comfort with the aim of providing experimental evidence for the proposed causal link between these emotions and intentions to engage in social competition. Results showed that lower levels of security-comfort reduced women's readiness to compete socially with men. Experiment 2 investigated the effect of hostile sexism on women's emotional reactions and readiness to engage in social competition. Consistent with the proposed model, results showed that exposure to hostile beliefs about women (1) increased anger-frustration and (2) decreased security-comfort. More specifically, exposure to hostile sexism had a positive indirect effect on social competition intentions through anger-frustration, and a negative indirect effect through security-comfort. © 2015 The British Psychological Society.

Competition and quality in health care markets: a differential-game approach.

PubMed

Brekke, Kurt R; Cellini, Roberto; Siciliani, Luigi; Straume, Odd Rune

2010-07-01

We investigate the effect of competition on quality in health care markets with regulated prices taking a differential game approach, in which quality is a stock variable. Using a Hotelling framework, we derive the open-loop solution (health care providers set the optimal investment plan at the initial period) and the feedback closed-loop solution (providers move investments in response to the dynamics of the states). Under the closed-loop solution competition is more intense in the sense that providers observe quality in each period and base their investment on this information. If the marginal provision cost is constant, the open-loop and closed-loop solutions coincide, and the results are similar to the ones obtained by static models. If the marginal provision cost is increasing, investment and quality are lower in the closed-loop solution (when competition is more intense). In this case, static models tend to exaggerate the positive effect of competition on quality.

Good practices in health care "management experimentation models": insights from an international public-private partnership on transplantation and advanced specialized therapies.

PubMed

Longo, Maria Cristina

2015-01-01

The research analyzes good practices in health care "management experimentation models," which fall within the broader range of the integrative public-private partnerships (PPPs). Introduced by the Italian National Healthcare System in 1991, the "management experimentation models" are based on a public governance system mixed with a private management approach, a patient-centric orientation, a shared financial risk, and payment mechanisms correlated with clinical outcomes, quality, and cost-savings. This model makes public hospitals more competitive and efficient without affecting the principles of universal coverage, solidarity, and equity of access, but requires higher financial responsibility for managers and more flexibility in operations. In Italy the experience of such experimental models is limited but successful. The study adopts the case study methodology and refers to the international collaboration started in 1997 between two Italian hospitals and the University of Pittsburgh Medical Center (UPMC - Pennsylvania, USA) in the field of organ transplants and biomedical advanced therapies. The research allows identifying what constitutes good management practices and factors associated with higher clinical performance. Thus, it allows to understand whether and how the management experimentation model can be implemented on a broader basis, both nationwide and internationally. However, the implementation of integrative PPPs requires strategic, cultural, and managerial changes in the way in which a hospital operates; these transformations are not always sustainable. The recognition of ISMETT's good management practices is useful for competitive benchmarking among hospitals specialized in organ transplants and for its insights on the strategies concerning the governance reorganization in the hospital setting. Findings can be used in the future for analyzing the cross-country differences in productivity among well-managed public hospitals.

An analytically tractable model for community ecology with many species

NASA Astrophysics Data System (ADS)

Dickens, Benjamin; Fisher, Charles; Mehta, Pankaj; Pankaj Mehta Biophysics Theory Group Team

A fundamental problem in community ecology is to understand how ecological processes such as selection, drift, and immigration yield observed patterns in species composition and diversity. Here, we present an analytically tractable, presence-absence (PA) model for community assembly and use it to ask how ecological traits such as the strength of competition, diversity in competition, and stochasticity affect species composition in a community. In our PA model, we treat species as stochastic binary variables that can either be present or absent in a community: species can immigrate into the community from a regional species pool and can go extinct due to competition and stochasticity. Despite its simplicity, the PA model reproduces the qualitative features of more complicated models of community assembly. In agreement with recent work on large, competitive Lotka-Volterra systems, the PA model exhibits distinct ecological behaviors organized around a special (``critical'') point corresponding to Hubbell's neutral theory of biodiversity. Our results suggest that the concepts of ``phases'' and phase diagrams can provide a powerful framework for thinking about community ecology and that the PA model captures the essential ecological dynamics of community assembly. Pm was supported by a Simons Investigator in the Mathematical Modeling of Living Systems and a Sloan Research Fellowship.

Modeling strategic competition in hydro-thermal electricity generation markets with cascaded reservoir-hydroelectric generation plants

NASA Astrophysics Data System (ADS)

Uluca, Basak

This dissertation aims to achieve two goals. The first is to model the strategic interactions of firms that own cascaded reservoir-hydro plants in oligopolistic and mixed oligopolistic hydrothermal electricity generation markets. Although competition in thermal generation has been extensively modeled since the beginning of deregulation, the literature on competition in hydro generation is still limited; in particular, equilibrium models of oligopoly that study the competitive behavior of firms that own reservoir-hydro plants along the same river in hydrothermal electricity generation markets are still under development. In competitive markets, when the reservoirs are located along the same river, the water released from an upstream reservoir for electricity generation becomes input to the immediate downstream reservoir, which may be owned by a competitor, for current or future use. To capture the strategic interactions among firms with cascaded reservoir-hydro plants, the Upstream-Conjecture approach is proposed. Under the Upstream-Conjecture approach, a firm with an upstream reservoir-hydro plant assumes that firms with downstream reservoir-hydro plants will respond to changes in the upstream firm's water release by adjusting their water release by the same amount. The results of the Upstream Conjecture experiments indicate that firms that own upstream reservoirs in a cascade may have incentive to withhold or limit hydro generation, forcing a reduction in the utilization of the downstream hydro generation plants that are owned by competitors. Introducing competition to hydroelectricity generation markets is challenging and ownership allocation of the previously state-owned cascaded reservoir-hydro plants through privatization can have significant impact on the competitiveness of the generation market. The second goal of the dissertation is to extract empirical guidance about best policy choices for the ownership of the state-owned generation plants, including the cascaded reservoir-hydro plants. Specifically, an equilibrium model of oligopoly, where only private firms compete for electricity supply is proposed. Since some electricity generation markets are better characterized as mixed oligopolies, where the public firm coexists with the private firms for electricity supply, and not as oligopolies, another equilibrium model of mixed oligopoly is proposed. The proposed mixed oligopoly equilibrium model is the first implementation of such market structure in electricity markets. The mathematical models developed in this research are applied to the simplified representation of the Turkish electricity generation market to investigate the impact of various ownership allocation scenarios that may result from the privatization of the state owned generation plants, including the cascaded reservoir-hydro plants, on the competitive market outcomes.

Risk equalization, competition, and choice: a preliminary assessment of the 1993 German health reforms.

PubMed

Wysong, J A; Abel, T

1996-01-01

Risk adjustment and/or equalization has become a central issue in the health care reform initiatives of many countries, including Germany, Switzerland, the Netherlands, Israel, the U.K. and the U.S. Risk adjustment is widely seen as essential to prevent cream skimming and to promote fair competition. In this vein, the 1993 German health reforms require implementation of a risk-based contribution rate equalization scheme by 1996. This paper provides a preliminary assessment of the risk equalization methodology currently proposed for Germany. Recent research in the U.S. and the Netherlands is used to examine whether the sociodemographic factors being used in Germany are likely to be effective. Research findings from both countries indicate that risk formulas based only on socio-demographic factors predict only one-tenth to one-fourth of the maximum possible explainable variance. If the current formula is used, sickness funds with higher concentrations of high risk groups are likely to be substantially under compensated, and to face serious enrollment and financial problems. The authors conclude that improvements in the formula through measures based on diagnosis and prior hospitalization, disability status, and regional variations in utilization and cost are urgently needed before the system is implemented. The German experience is also relevant to other countries that have relied to date on socio-demographic measures for risk adjustment.

Impact of competitor species composition on predicting diameter growth and survival rates of Douglas-fir trees in southwestern Oregon

USGS Publications Warehouse

Bravo, Felipe; Hann, D.W.; Maguire, Douglas A.

2001-01-01

Mixed conifer and hardwood stands in southwestern Oregon were studied to explore the hypothesis that competition effects on individual-tree growth and survival will differ according to the species comprising the competition measure. Likewise, it was hypothesized that competition measures should extrapolate best if crown-based surrogates are given preference over diameter-based (basal area based) surrogates. Diameter growth and probability of survival were modeled for individual Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees growing in pure stands. Alternative models expressing one-sided and two-sided competition as a function of either basal area or crown structure were then applied to other plots in which Douglas-fir was mixed with other conifers and (or) hardwood species. Crown-based variables outperformed basal area based variables as surrogates for one-sided competition in both diameter growth and survival probability, regardless of species composition. In contrast, two-sided competition was best represented by total basal area of competing trees. Surrogates reflecting differences in crown morphology among species relate more closely to the mechanics of competition for light and, hence, facilitate extrapolation to species combinations for which no observations are available.

Elevated carbon dioxide is predicted to promote coexistence among competing species in a trait-based model

DOE PAGES

Ali, Ashehad A.; Medlyn, Belinda E.; Aubier, Thomas G.; ...

2015-10-06

Differential species responses to atmospheric CO 2 concentration (C a) could lead to quantitative changes in competition among species and community composition, with flow-on effects for ecosystem function. However, there has been little theoretical analysis of how elevated C a (eC a) will affect plant competition, or how composition of plant communities might change. Such theoretical analysis is needed for developing testable hypotheses to frame experimental research. Here, we investigated theoretically how plant competition might change under eC a by implementing two alternative competition theories, resource use theory and resource capture theory, in a plant carbon and nitrogen cycling model.more » The model makes several novel predictions for the impact of eC a on plant community composition. Using resource use theory, the model predicts that eC a is unlikely to change species dominance in competition, but is likely to increase coexistence among species. Using resource capture theory, the model predicts that eC a may increase community evenness. Collectively, both theories suggest that eC a will favor coexistence and hence that species diversity should increase with eC a. Our theoretical analysis leads to a novel hypothesis for the impact of eC a on plant community composition. In this study, the hypothesis has potential to help guide the design and interpretation of eC a experiments.« less

Developing a framework for energy technology portfolio selection

NASA Astrophysics Data System (ADS)

Davoudpour, Hamid; Ashrafi, Maryam

2012-11-01

Today, the increased consumption of energy in world, in addition to the risk of quick exhaustion of fossil resources, has forced industrial firms and organizations to utilize energy technology portfolio management tools viewed both as a process of diversification of energy sources and optimal use of available energy sources. Furthermore, the rapid development of technologies, their increasing complexity and variety, and market dynamics have made the task of technology portfolio selection difficult. Considering high level of competitiveness, organizations need to strategically allocate their limited resources to the best subset of possible candidates. This paper presents the results of developing a mathematical model for energy technology portfolio selection at a R&D center maximizing support of the organization's strategy and values. The model balances the cost and benefit of the entire portfolio.

Carbon pricing, nuclear power and electricity markets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cameron, R.; Keppler, J. H.

2012-07-01

In 2010, the NEA in conjunction with the International Energy Agency produced an analysis of the Projected Costs of Electricity for almost 200 power plants, covering nuclear, fossil fuel and renewable electricity generation. That analysis used lifetime costs to consider the merits of each technology. However, the lifetime cost analysis is less applicable in liberalised markets and does not look specifically at the viewpoint of the private investor. A follow-up NEA assessment of the competitiveness of nuclear energy against coal- and gas-fired generation under carbon pricing has considered just this question. The economic competition in electricity markets is today betweenmore » nuclear energy and gas-fired power generation, with coal-fired power generation not being competitive as soon as even modest carbon pricing is introduced. Whether nuclear energy or natural gas comes out ahead in their competition depends on a number of assumptions, which, while all entirely reasonable, yield very different outcomes. The analysis in this study has been developed on the basis of daily data from European power markets over the last five-year period. Three different methodologies, a Profit Analysis looking at historic returns over the past five years, an Investment Analysis projecting the conditions of the past five years over the lifetime of plants and a Carbon Tax Analysis (differentiating the Investment Analysis for different carbon prices) look at the issue of competitiveness from different angles. They show that the competitiveness of nuclear energy depends on a number of variables which in different configurations determine whether electricity produced from nuclear power or from CCGTs generates higher profits for its investors. These are overnight costs, financing costs, gas prices, carbon prices, profit margins (or mark-ups), the amount of coal with carbon capture and electricity prices. This paper will present the outcomes of the analysis in the context of a liberalised electricity market, looking at the impact of the seven key variables and provide conclusions on the portfolio that a utility would be advised to maintain, given the need to limit risks but also to move to low carbon power generation. Such portfolio diversification would not only limit financial investor risk, but also a number of non-financial risks (climate change, security of supply, accidents). (authors)« less

Clean Energy Manufacturing Initiative Solid-State Lighting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Sunil; Edmond, John; Krames, Michael

2014-09-23

The importance of U.S. manufacturing for clean energy technologies, such as solid-state lighting (SSL), is paramount to increasing competitiveness in a global marketplace. SSLs are poised to drive the lighting market, worldwide. In order to continue that competitiveness and support further innovation, the time to invest in U.S. manufacturing of clean energy technologies is now. Across the country, companies developing innovative clean energy technologies find competitive advantages to manufacturing in the U.S. The Department of Energy's Building Technology Office SSL Manufacturing Roadmap is just one example of how we support manufacturing through convening industry perspectives on opportunities to significantly reducemore » risk, improve quality, increase yields, and lower costs.« less

Clean Energy Manufacturing Initiative Solid-State Lighting Video

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Sunil; Edmond, John; Krames, Michael

2014-09-23

The importance of U.S. manufacturing for clean energy technologies, such as solid-state lighting (SSL), is paramount to increasing competitiveness in a global marketplace. SSLs are poised to drive the lighting market, worldwide. In order to continue that competitiveness and support further innovation, the time to invest in U.S. manufacturing of clean energy technologies is now. Across the country, companies developing innovative clean energy technologies find competitive advantages to manufacturing in the U.S. The Department of Energy's Building Technology Office SSL Manufacturing Roadmap is just one example of how we support manufacturing through convening industry perspectives on opportunities to significantly reducemore » risk, improve quality, increase yields, and lower costs.« less

Clean Energy Manufacturing Initiative Solid-State Lighting Video

ScienceCinema

Thomas, Sunil; Edmond, John; Krames, Michael; Raman, Sudhakar

2018-01-16

The importance of U.S. manufacturing for clean energy technologies, such as solid-state lighting (SSL), is paramount to increasing competitiveness in a global marketplace. SSLs are poised to drive the lighting market, worldwide. In order to continue that competitiveness and support further innovation, the time to invest in U.S. manufacturing of clean energy technologies is now. Across the country, companies developing innovative clean energy technologies find competitive advantages to manufacturing in the U.S. The Department of Energy's Building Technology Office SSL Manufacturing Roadmap is just one example of how we support manufacturing through convening industry perspectives on opportunities to significantly reduce risk, improve quality, increase yields, and lower costs.

Price Analysis and the Effects of Competition.

DTIC Science & Technology

1985-10-01

state of the market . For instance, is it possible that competition can squeeze a company to greater efficiency or lower profits in the short run, but...dual- source competition . The Stackelberg model recognizes two types of firm behavior. A firm may choose to be a leader and pursue a dominant market ...strate- gies in areas of potential competition . In this instance, the follower firm will serve that segment of the market that the leader firm cannot

Competitive intransitivity promotes species coexistence.

PubMed

Laird, Robert A; Schamp, Brandon S

2006-08-01

Using a spatially explicit cellular automaton model with local competition, we investigate the potential for varied levels of competitive intransitivity (i.e., nonhierarchical competition) to promote species coexistence. As predicted, on average, increased levels of intransitivity result in more sustained coexistence within simulated communities, although the outcome of competition also becomes increasingly unpredictable. Interestingly, even a moderate degree of intransitivity within a community can promote coexistence, in terms of both the length of time until the first competitive exclusion and the number of species remaining in the community after 500 simulated generations. These results suggest that modest levels of intransitivity in nature, such as those that are thought to be characteristic of plant communities, can contribute to coexistence and, therefore, community-scale biodiversity. We explore a potential connection between competitive intransitivity and neutral theory, whereby competitive intransitivity may represent an important mechanism for "ecological equivalence."

A nonlinear competitive model of the prostate tumor growth under intermittent androgen suppression.

PubMed

Yang, Jing; Zhao, Tong-Jun; Yuan, Chang-Qing; Xie, Jing-Hui; Hao, Fang-Fang

2016-09-07

Hormone suppression has been the primary modality of treatment for prostate cancer. However long-term androgen deprivation may induce androgen-independent (AI) recurrence. Intermittent androgen suppression (IAS) is a potential way to delay or avoid the AI relapse. Mathematical models of tumor growth and treatment are simple while they are capable of capturing the essence of complicated interactions. Game theory models have analyzed that tumor cells can enhance their fitness by adopting genetically determined survival strategies. In this paper, we consider the survival strategies as the competitive advantage of tumor cells and propose a new model to mimic the prostate tumor growth in IAS therapy. Then we investigate the competition effect in tumor development by numerical simulations. The results indicate that successfully IAS-controlled states can be achieved even though the net growth rate of AI cells is positive for any androgen level. There is crucial difference between the previous models and the new one in the phase diagram of successful and unsuccessful tumor control by IAS administration, which means that the suggestions from the models for medication can be different. Furthermore we introduce quadratic logistic terms to the competition model to simulate the tumor growth in the environment with a finite carrying capacity considering the nutrients or inhibitors. The simulations show that the tumor growth can reach an equilibrium state or an oscillatory state with the net growth rate of AI cells being androgen independent. Our results suggest that the competition and the restraint of a limited environment can enhance the possibility of relapse prevention. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Path Model of Factors Affecting Secondary School Students' Technological Literacy

ERIC Educational Resources Information Center

Avsec, Stanislav; Jamšek, Janez

2018-01-01

Technological literacy defines a competitive vision for technology education. Working together with competitive supremacy, technological literacy shapes the actions of technology educators. Rationalised by the dictates of industry, technological literacy was constructed as a product of the marketplace. There are many models that visualise…

Overemphasis on Perfectly Competitive Markets in Microeconomics Principles Textbooks

ERIC Educational Resources Information Center

Hill, Roderick; Myatt, Anthony

2007-01-01

Microeconomic principles courses focus on perfectly competitive markets far more than other market structures. The authors examine five possible reasons for this but find none of them sufficiently compelling. They conclude that textbook authors should place more emphasis on how economists select appropriate models and test models' predictions…

Cost modeling of biocontrol strains Pseudomonas chlororaphis and P. flurorescens for competitive exclusion of Salmonella enterica on tomatoes

USDA-ARS?s Scientific Manuscript database

Biological control of foodborne pathogens may complement postharvest intervention measures to enhance food safety of minimally processed produce. The purpose of this research was to develop cost model estimates for application of competitive exclusion process (CEM) using Pseudomonas chlororaphis and...

Dynamics of the antibody-T.cruzi competition during Chagas infection: Prognostic relevance of intracellular replication

NASA Astrophysics Data System (ADS)

Sibona, G. J.; Condat, C. A.; Isasi, S. Cossy

2005-02-01

A recently proposed model for the competitive parasite-antibody interactions in Chagas disease is extended by separately describing the parasitic intracellular and extracellular phases. The model solutions faithfully reproduce available population data and yield predictions for parasite-induced cardiac cell damage.

e-Learning Risks: Why Universities Should NOT Go It Alone

ERIC Educational Resources Information Center

Matthews, Tim; Pickar, Gloria; Schneid, Tom

2007-01-01

With $1M, faculty support, and their reputation at risk, Eastern Kentucky University (EKU) sought a distance learning partner to assess the MS in Loss Prevention & Safety opportunity, and then market the program to qualified students ready to learn. This compelling case study demonstrates how marketplace demand and competitive advantage can…

SAD effects on grantsmanship.

PubMed

Lozano, George A

2015-01-01

SAD is a state of depression induced by a lack of sufficient sunlight that occurs at high latitudes during the fall and winter. SAD causes people to be risk-adverse. Granting agencies of high latitude countries should time high-risk research competitions so they do not coincide with the SAD months. © 2015 WILEY Periodicals, Inc.

DOD Competitive Sourcing: Questions About Goals, Pace, and Risks of Key Reform Initiative.

DTIC Science & Technology

1999-02-01

internal audit , and the function being studied. To the extent existing in-house resources are limited, if resources need to be shifted to meet new...contractor support costs and $24 million for existing in-house staff—to compete 4,000 positions in a multifunction, multilocation study, at least $7,000...competitions and of personnel separation costs on their installations. Army officials, based on work by the Army Audit Agency, have expressed concern that

Pollinator Competition as a Driver of Floral Divergence: An Experimental Test.

PubMed

Temeles, Ethan J; Newman, Julia T; Newman, Jennifer H; Cho, Se Yeon; Mazzotta, Alexandra R; Kress, W John

2016-01-01

Optimal foraging models of floral divergence predict that competition between two different types of pollinators will result in partitioning, increased assortative mating, and divergence of two floral phenotypes. We tested these predictions in a tropical plant-pollinator system using sexes of purple-throated carib hummingbirds (Anthracothorax jugularis) as the pollinators, red and yellow inflorescence morphs of Heliconia caribaea as the plants, and fluorescent dyes as pollen analogs in an enclosed outdoor garden. When foraging alone, males exhibited a significant preference for the yellow morph of H. caribaea, whereas females exhibited no preference. In competition, males maintained their preference for the yellow morph and through aggression caused females to over-visit the red morph, resulting in resource partitioning. Competition significantly increased within-morph dye transfer (assortative mating) relative to non-competitive environments. Competition and partitioning of color morphs by sexes of purple-throated caribs also resulted in selection for floral divergence as measured by dye deposition on stigmas. Red and yellow morphs did not differ significantly in dye deposition in the competition trials, but differences in dye deposition and preferences for morphs when sexes of purple-throated caribs foraged alone implied fixation of one or the other color morph in the absence of competition. Competition also resulted in selection for divergence in corolla length, with the red morph experiencing directional selection for longer corollas and the yellow morph experiencing stabilizing selection on corolla length. Our results thus support predictions of foraging models of floral divergence and indicate that pollinator competition is a viable mechanism for divergence in floral traits of plants.

Pollinator Competition as a Driver of Floral Divergence: An Experimental Test

PubMed Central

Temeles, Ethan J.; Newman, Julia T.; Newman, Jennifer H.; Cho, Se Yeon; Mazzotta, Alexandra R.; Kress, W. John

2016-01-01

Optimal foraging models of floral divergence predict that competition between two different types of pollinators will result in partitioning, increased assortative mating, and divergence of two floral phenotypes. We tested these predictions in a tropical plant-pollinator system using sexes of purple-throated carib hummingbirds (Anthracothorax jugularis) as the pollinators, red and yellow inflorescence morphs of Heliconia caribaea as the plants, and fluorescent dyes as pollen analogs in an enclosed outdoor garden. When foraging alone, males exhibited a significant preference for the yellow morph of H. caribaea, whereas females exhibited no preference. In competition, males maintained their preference for the yellow morph and through aggression caused females to over-visit the red morph, resulting in resource partitioning. Competition significantly increased within-morph dye transfer (assortative mating) relative to non-competitive environments. Competition and partitioning of color morphs by sexes of purple-throated caribs also resulted in selection for floral divergence as measured by dye deposition on stigmas. Red and yellow morphs did not differ significantly in dye deposition in the competition trials, but differences in dye deposition and preferences for morphs when sexes of purple-throated caribs foraged alone implied fixation of one or the other color morph in the absence of competition. Competition also resulted in selection for divergence in corolla length, with the red morph experiencing directional selection for longer corollas and the yellow morph experiencing stabilizing selection on corolla length. Our results thus support predictions of foraging models of floral divergence and indicate that pollinator competition is a viable mechanism for divergence in floral traits of plants. PMID:26814810

Administrative Coordination in Non-Profit Human Service Delivery Networks: The Role of Competition and Trust

PubMed Central

Bunger, Alicia C.

2014-01-01

Non-profit human service organizations operating within the same regional network are often faced with dual pressure to compete as well as coordinate administrative operations (by sharing funding, staff or space) to enhance efficiency. Emerging evidence has demonstrated that competing organizations coordinate, despite the risks. Trust, or perceived trustworthiness between two organizations may mitigate the negative influence of competition on coordination, however there have been few explicit tests of this hypothesis among non-profit organizations. Drawing on quantitative data collected from a network of 36 non-profit children’s behavioral health organizations, this paper empirically tests how competition and perceived trustworthiness interact to influence administrative coordination. Results support the hypothesis that trustworthiness moderates the influence of competition on administrative coordination. Findings suggest that as competing non-profit leaders build trust, the more their agencies coordinate their administrative functions. This study highlights the importance of leaders’ perceptions for organizational strategy. PMID:25349468

Printed Wiring Board Cleaner Technologies Substitutes Assessment: Making Holes Conductive

EPA Pesticide Factsheets

This document presents comparative risk, competitiveness, and resource requirements on technologies for performing the “making holes conductive” function during printed wiring board manufacturing.

Gamification and Microlearning for Engagement With Quality Improvement (GAMEQI): A Bundled Digital Intervention for the Prevention of Central Line-Associated Bloodstream Infection.

PubMed

Orwoll, Benjamin; Diane, Shelley; Henry, Duncan; Tsang, Lisa; Chu, Kristin; Meer, Carrie; Hartman, Kevin; Roy-Burman, Arup

Central line-associated bloodstream infections (CLABSIs) cause major patient harm, preventable through attention to line care best practice standards. The objective was to determine if a digital self-assessment application (CLABSI App), bundling line care best practices with social gamification and in-context microlearning, could engage nurses in CLABSI prevention. Nurses caring for children with indwelling central venous catheters in 3 high-risk units were eligible to participate. All other units served as controls. The intervention was a 12-month nonrandomized quality improvement study of CLABSI App implementation with interunit competitions. Compared to the preceding year, the intervention group (9886 line days) CLABSI rate decreased by 48% ( P = .03). Controls (7879 line days) did not change significantly. In all, 105 unique intervention group nurses completed 673 self-assessments. Competitions were associated with increased engagement as measured by self-assessments and unique participants. This model could be extended to other health care-associated infections, and more broadly to process improvement within and across health care systems.

Insect herbivores change the outcome of plant competition through both inter- and intraspecific processes.

PubMed

Kim, Tania N; Underwood, Nora; Inouye, Brian D

2013-08-01

Insect herbivores can affect plant abundance and community composition, and theory suggests that herbivores influence plant communities by altering interspecific interactions among plants. Because the outcome of interspecific interactions is influenced by the per capita competitive ability of plants, density dependence, and intrinsic rates of increase, measuring herbivore effects on all these processes is necessary to understand the mechanisms by which herbivores influence plant communities. We fit alternative competition models to data from a response surface experiment conducted over four years to examine how herbivores affected the outcome of competition between two perennial plants, Solidago altissima and Solanum carolinense. Within a growing season, herbivores reduced S. carolinense plant size but did not affect the size of S. altissima, which exhibited compensatory growth. Across seasons, herbivores did not affect S. carolinense density or biomass but reduced both the density and population growth of S. altissima. The best-fit models indicated that the effects of herbivores varied with year. In some years, herbivores increased the per capita competitive effect of S. altissima on S. carolinense; in other years, herbivores influenced the intrinsic rate of increase of S. altissima. We examined possible herbivore effects on the longer-term outcome of competition (over the time scale of a typical old-field habitat), using simulations based on the best-fit models. In the absence of herbivores, plant coexistence was observed. In the presence of herbivores, S. carolinense was excluded by S. altissima in 72.3% of the simulations. We demonstrate that herbivores can influence the outcome of competition through changes in both per capita competitive effects and intrinsic rates of increase. We discuss the implications of these results for ecological succession and biocontrol.

Market Competitiveness Evaluation of Mechanical Equipment with a Pairwise Comparisons Hierarchical Model.

PubMed

Hou, Fujun

2016-01-01

This paper provides a description of how market competitiveness evaluations concerning mechanical equipment can be made in the context of multi-criteria decision environments. It is assumed that, when we are evaluating the market competitiveness, there are limited number of candidates with some required qualifications, and the alternatives will be pairwise compared on a ratio scale. The qualifications are depicted as criteria in hierarchical structure. A hierarchical decision model called PCbHDM was used in this study based on an analysis of its desirable traits. Illustration and comparison shows that the PCbHDM provides a convenient and effective tool for evaluating the market competitiveness of mechanical equipment. The researchers and practitioners might use findings of this paper in application of PCbHDM.

Measuring Men's Gender Norms and Gender Role Conflict/Stress in a High HIV-Prevalence South African Setting.

PubMed

Gottert, Ann; Barrington, Clare; Pettifor, Audrey; McNaughton-Reyes, Heath Luz; Maman, Suzanne; MacPhail, Catherine; Kahn, Kathleen; Selin, Amanda; Twine, Rhian; Lippman, Sheri A

2016-08-01

Gender norms and gender role conflict/stress may influence HIV risk behaviors among men; however scales measuring these constructs need further development and evaluation in African settings. We conducted exploratory and confirmatory factor analyses to evaluate the Gender Equitable Men's Scale (GEMS) and the Gender Role Conflict/Stress (GRC/S) scale among 581 men in rural northeast South Africa. The final 17-item GEMS was unidimensional, with adequate model fit and reliability (alpha = 0.79). Factor loadings were low (0.2-0.3) for items related to violence and sexual relationships. The final 24-item GRC/S scale was multidimensional with four factors: Success, power, competition; Subordination to women; Restrictive emotionality; and Sexual prowess. The scale had adequate model fit and good reliability (alpha = 0.83). While GEMS is a good measure of inequitable gender norms, new or revised scale items may need to be explored in the South African context. Adding the GRC/S scale to capture men's strain related to gender roles could provide important insights into men's risk behaviors.

A model of risk and mental state shifts during social interaction.

PubMed

Hula, Andreas; Vilares, Iris; Lohrenz, Terry; Dayan, Peter; Montague, P Read

2018-02-01

Cooperation and competition between human players in repeated microeconomic games offer a window onto social phenomena such as the establishment, breakdown and repair of trust. However, although a suitable starting point for the quantitative analysis of such games exists, namely the Interactive Partially Observable Markov Decision Process (I-POMDP), computational considerations and structural limitations have limited its application, and left unmodelled critical features of behavior in a canonical trust task. Here, we provide the first analysis of two central phenomena: a form of social risk-aversion exhibited by the player who is in control of the interaction in the game; and irritation or anger, potentially exhibited by both players. Irritation arises when partners apparently defect, and it potentially causes a precipitate breakdown in cooperation. Failing to model one's partner's propensity for it leads to substantial economic inefficiency. We illustrate these behaviours using evidence drawn from the play of large cohorts of healthy volunteers and patients. We show that for both cohorts, a particular subtype of player is largely responsible for the breakdown of trust, a finding which sheds new light on borderline personality disorder.

A model of risk and mental state shifts during social interaction

PubMed Central

Vilares, Iris

2018-01-01

Cooperation and competition between human players in repeated microeconomic games offer a window onto social phenomena such as the establishment, breakdown and repair of trust. However, although a suitable starting point for the quantitative analysis of such games exists, namely the Interactive Partially Observable Markov Decision Process (I-POMDP), computational considerations and structural limitations have limited its application, and left unmodelled critical features of behavior in a canonical trust task. Here, we provide the first analysis of two central phenomena: a form of social risk-aversion exhibited by the player who is in control of the interaction in the game; and irritation or anger, potentially exhibited by both players. Irritation arises when partners apparently defect, and it potentially causes a precipitate breakdown in cooperation. Failing to model one’s partner’s propensity for it leads to substantial economic inefficiency. We illustrate these behaviours using evidence drawn from the play of large cohorts of healthy volunteers and patients. We show that for both cohorts, a particular subtype of player is largely responsible for the breakdown of trust, a finding which sheds new light on borderline personality disorder. PMID:29447153

Integrated approach for managing health risks at work--the role of occupational health nurses.

PubMed

Marinescu, Luiza G

2007-02-01

Currently, many organizations are using a department-centered approach to manage health risks at work. In such a model, segregated departments are providing employee benefits such as health insurance, workers' compensation, and short- and long-term disability or benefits addressing work-life issues. In recent years, a new model has emerged: health and productivity management (HPM). This is an employee-centered, integrated approach, designed to increase efficiency, reduce competition for scarce resources, and increase employee participation in prevention activities. Evidence suggests that corporations using integrated HPM programs achieve better health outcomes for their employees, with consequent increased productivity and decreased absenteeism. Occupational health nurses are well positioned to assume leadership roles in their organizations by coordinating efforts and programs across departments that offer health, wellness, and safety benefits. To assume their role as change agents to improve employees' health, nurses should start using the language of business more often by improving their communication skills, computer skills, and ability to quantify and articulate results of programs and services to senior management.

Risk assessment in the upstream crude oil supply chain: Leveraging analytic hierarchy process

NASA Astrophysics Data System (ADS)

Briggs, Charles Awoala

For an organization to be successful, an effective strategy is required, and if implemented appropriately the strategy will result in a sustainable competitive advantage. The importance of decision making in the oil industry is reflected in the magnitude and nature of the industry. Specific features of the oil industry supply chain, such as its longer chain, the complexity of its transportation system, its complex production and storage processes, etc., pose challenges to its effective management. Hence, understanding the risks, the risk sources, and their potential impacts on the oil industry's operations will be helpful in proposing a risk management model for the upstream oil supply chain. The risk-based model in this research uses a three-level analytic hierarchy process (AHP), a multiple-attribute decision-making technique, to underline the importance of risk analysis and risk management in the upstream crude oil supply chain. Level 1 represents the overall goal of risk management; Level 2 is comprised of the various risk factors; and Level 3 represents the alternative criteria of the decision maker as indicated on the hierarchical structure of the crude oil supply chain. Several risk management experts from different oil companies around the world were surveyed, and six major types of supply chain risks were identified: (1) exploration and production, (2) environmental and regulatory compliance, (3) transportation, (4) availability of oil, (5) geopolitical, and (6) reputational. Also identified are the preferred methods of managing risks which include; (1) accept and control the risks, (2) avoid the risk by stopping the activity, or (3) transfer or share the risks to other companies or insurers. The results from the survey indicate that the most important risk to manage is transportation risk with a priority of .263, followed by exploration/production with priority of .198, with an overall inconsistency of .03. With respect to major objectives the most preferred risk management policy option based on the result of the composite score is accept and control risk with a priority of .446, followed by transfer or share risk with a priority of .303. The least likely option is to terminate or forgo activity with a priority of .251.